Many stir drink excessively (7)
I believe the answer is:
carouse
'drink excessively' is the definition.
'carouse' can be an answer for 'drink' (thesaurus). I'm not sure about the 'excessively' bit.
'many stir' is the wordplay.
I cannot really understand how this works, but
'many' could be 'c' (C is the Roman numeral for 100) and 'c' is found within the answer.
'stir' could be 'arouse' (arousing is a kind of stirring) and 'arouse' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for carouse that I've seen before include "Celebrate noisily" , "booze" , "Roister" , "Drink freely and noisily" , "Take a course to party wildly" .)