The answer is DRAWBACK, eight letters. At five squares it is MINUS and at three it is CON. This clue is unusual in that the candidate list is spread evenly across a wide range of lengths, so the square count alone narrows it faster than almost any other reasoning you can apply.
Three different ideas wearing one word
Disadvantage can be a property of a thing, a position a person is in, or a burden imposed on someone. Those three readings do not share a vocabulary.
A property of a thing is the commonest reading and gives DRAWBACK, DOWNSIDE, MINUS, CON, SNAG and CATCH. Something is good except for this one problem. A position gives HANDICAP and the phrase about being at a disadvantage, where the disadvantage is relative to someone else rather than built into the thing itself. A burden gives PENALTY, LIABILITY and DETRIMENT, which carry a sense of cost being applied. With nothing but the bare noun to work from, bet on the first group.
Eight squares down to three
Count before you choose:
| Letters | Answer | What triggers it |
|---|---|---|
| 3 | CON | Paired with pro, as in pros and cons |
| 4 | SNAG | A problem that appears partway through |
| 5 | MINUS | Paired with plus, often in a list of two |
| 5 | CATCH | The hidden condition in an offer |
| 7 | DEMERIT | The formal opposite of merit |
| 8 | DRAWBACK | The plain default for the bare clue |
| 8 | DOWNSIDE | The same idea in newer register |
| 8 | HANDICAP | A disadvantage relative to competitors |
| 9 | DETRIMENT | Harm, often in a formal or legal surface |
| 9 | HINDRANCE | Something that slows progress |
| 9 | LIABILITY | A person or thing that costs you |
Three of the eight letter options are common enough that eight squares does not settle it on its own. DRAWBACK is the plain choice, DOWNSIDE turns up when the clue surface is modern and businesslike, and HANDICAP needs a competitive reading somewhere in the wording.

Con and minus are borrowed from pairings
CON and MINUS both work as disadvantage words only because each has a partner. Con means disadvantage because pro means advantage, and the pair comes to English from Latin, where the phrase sets for and against side by side. Minus means disadvantage because plus means advantage, and the arithmetic sense supplies the direction. Neither word would carry the meaning alone.
That matters when you are solving, because it tells you what a setter has to do to reach them. A clue aiming at CON tends to mention a list, a debate, or the other column. A clue aiming at MINUS often mentions a plus explicitly. When the clue offers a naked noun and no other hook, the longer plain synonyms are more likely than either of these.
Catch and snag point at something concealed
These two are not general purpose synonyms and should not be treated as such. A catch is a disadvantage that was hidden inside something presented as good, which is why the question about what the catch is only makes sense when an offer looks too generous. A snag is a problem that turns up in the middle of something already under way, and the metaphor is physical, from cloth caught on a projection.
Both are therefore weak answers to a clue that presents disadvantage in the abstract and strong ones to a clue describing somebody discovering the problem late. Read the surface for whether anyone is being surprised. If the clue could be spoken by a person who has just reached the small print, CATCH moves to the front of the list.
The prefix trick that solves it from one letter
English builds negative nouns with a small set of prefixes, and disadvantage words use several of them. DEMERIT starts with de, DETRIMENT with de, DOWNSIDE with down, DRAWBACK with draw. If your first crossing letter is D you have narrowed a long list to four in one move, and the square count finishes the job: seven for DEMERIT, eight for DOWNSIDE and DRAWBACK, nine for DETRIMENT. Getting a single reliable letter in a long slot is worth more here than in most clues, so solve the crossings before you keep staring at the definition.
Frequently asked questions
What is the three letter answer for Disadvantage?
CON, from the pairing of pros and cons. The clue usually hints at a list or a debate when this is the fill wanted.
Is DRAWBACK or DOWNSIDE the right eight letter answer?
Both fit and both are standard. DRAWBACK is the safer default, while DOWNSIDE tends to appear when the clue surface reads as modern or businesslike. A crossing letter separates them quickly.
When does Disadvantage mean HANDICAP?
When the disadvantage is relative to other people rather than built into a thing, such as in a race or a competition. HANDICAP is eight letters, the same as DRAWBACK and DOWNSIDE.