Something crafty in small cocktail (7)
I believe the answer is:
martini
'small cocktail' is the definition.
'martini' can be an answer for 'cocktail' (martini is a kind of cocktail). I am not certain of the 'small' bit.
'something crafty in' is the wordplay.
'something' becomes 'marti' (I can't explain this - if you can you should believe this answer much more).
'crafty' is an anagram indicator.
'in' is an anagram of 'ni'.
'marti'+'ni'='MARTINI'
Can you help me to learn more?
(Other definitions for martini that I've seen before include "In glass, one's dry" , "Italian drink" , "obtained from a bottle" , "alcoholic drink" , "Cocktail made with gin or vodka and vermouth" .)