Pal, mate (4)
I believe the answer is:
chum
I believe this clue is a double definition.
'pal' is the first definition.
(synonyms)
'mate' is the second definition.
(I've seen this before)
(Other definitions for chum that I've seen before include "Close friend (colloq.)" , "Pal, buddy" , "Salmon" , "Informally, a close friend" , "Pal, mate" .)