Skill evident in small cocktail (7)
I believe the answer is:
martini
'cocktail' is the definition.
(martini is a kind of cocktail)
'skill evident in small' is the wordplay.
'skill' becomes 'art' (I've seen this before).
'evident in' is an insertion indicator.
'small' becomes 'mini' (I've seen this before).
'art' placed inside 'mini' is 'MARTINI'.
(Other definitions for martini that I've seen before include "Type of Italian vermouth" , "Gin or vodka with dry vermouth" , "rifle" , "obtained from a bottle" , "Alternative name for Simone Memmi, pre-Renaissance Italian painter" .)