Being merry can be difficult! (5)

I believe the answer is:

tight

I'm a little stuck... Click here to teach me more about this clue!

'difficult' is the definition.
(similar in meaning)

I cannot understand how the rest of the clue works.

(Other definitions for tight that I've seen before include "Trim" , "It's not enough" , "Miserly (informal) - drunk (informal)" , "happy" , "reluctant to buy a round?" .)

I've seen this clue in the Evening Standard.

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