Clearly not a drink for slimmers (5)
I believe the answer is:
stout
'clearly not a drink' is the definition.
I can't tell whether this defines the answer.
'for slimmers' is the wordplay.
I cannot really understand how this works, but
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stout that I've seen before include "Heavily built; beer" , "tipple" , "Rather fat, stocky" , "of above-average weight" , "Round" .)