Bachelor remains for party (4)
I believe the answer is:
bash
'party' is the definition.
(I've seen this before)
'bachelor remains' is the wordplay.
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'remains' becomes 'ash' (I've seen this before).
'b'+'ash'='BASH'
'for' is the link.
(Other definitions for bash that I've seen before include "Hit hard; party (slang)" , "Shindig, function" , "Social event - clobber" , "Heavy blow; party" , "Party - whack" .)