More than one chum swallowing bait, briefly (6)
I believe the answer is:
plural
'more than' is the definition.
(I've seen this before)
'one chum swallowing bait briefly' is the wordplay.
'one chum' becomes 'pal' (both can mean a friend).
'swallowing' means one lot of letters goes inside another.
'bait' becomes 'lure' (synonyms).
'briefly' means to remove the last letter.
'lure' with its final letter taken off is 'lur'.
'pal' enclosing 'lur' is 'PLURAL'.
(Other definitions for plural that I've seen before include "More than one, not singular" , "Words such as "sheep" and "deer" (but not "cat" and "dog") can be this" , "Denotes more than one" , "Several" , "Numbering more than one" .)