A drink for Judy's companion (5)
I believe the answer is:
punch
'a drink' is the definition.
(punch is an alcoholic drink)
'judy's companion' is the wordplay.
'judy' becomes 'pun' (I can't explain this - if you can you should believe this answer much more).
'companion' becomes 'ch' (Companion of Honour).
'pun'+'ch'='PUNCH'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for punch that I've seen before include "Press" , "Sock" , "Hit - party drink" , "Slug - mixed drink" , "Strike, Judy's husband" .)