Gibe made by bachelor supporting pub (4)
I believe the answer is:
barb
'gibe' is the definition.
(both can mean an unkind comment)
'bachelor supporting pub' is the wordplay.
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'pub' becomes 'bar' (both are drinking establishments).
'b' after 'bar' is 'BARB'.
'made by' is the link.
(Other definitions for barb that I've seen before include "Woundingly pointed remark" , "Backward projecting point of an arrowhead" , "Jibe" , "Jag on a hook" , "Sharp point; wounding comment" .)