Enjoy a drink of whisky? Willingly! (4,1,4)
I believe the answer is:
like a shot
'willingly' is the definition.
(I've seen this before)
'enjoy a drink of whisky?' is the wordplay.
'enjoy' becomes 'like' (I've seen this in another clue).
'drink of whisky?' becomes 'shot'.
'like'+'a'+'shot'='LIKE A SHOT'
(Other definitions for like a shot that I've seen before include "show partiality for spirits" , "at the double?" , "What spirit drinkers do" , "sluggish?" , "At once, willingly" .)