Judge drops chorus (7)
I believe the answer is:
refrain
'chorus' is the definition.
(I know that chorus can be written as refrain)
'judge drops' is the wordplay.
'judge' becomes 'ref'.
'drops' becomes 'rain' (drops of water).
'ref'+'rain'='REFRAIN'
(Other definitions for refrain that I've seen before include "Don't do that - it's a song" , "Hold back" , "burden" , "Chorus; keep away (from)" , "Much repeated saying" .)