Finish after Friday, mate (6)
I believe the answer is:
friend
'mate' is the definition.
(mate can mean a friend)
'finish after friday' is the wordplay.
'finish' becomes 'end' (synonyms).
'after' is a charade indicator (letters next to each other).
'friday' becomes 'Fri' (synonyms).
'end' put after 'fri' is 'FRIEND'.
(Other definitions for friend that I've seen before include "Companion; Quaker" , "Ally, supporter" , "Close or intimate acquaintance" , "Person regarded with trust and affection" , "Comrade for finder" .)