Help in rewrite of brief, then finish (8)
I believe the answer is:
befriend
'help' is the definition.
(a friend might help another friend)
'rewrite of brief then finish' is the wordplay.
'rewrite of' indicates an anagram (letters rewritten in a new order).
'then' is a charade indicator (letters next to each other).
'finish' becomes 'end' (synonyms).
'brief' anagrammed gives 'befri'.
'befri'+'end'='BEFRIEND'
'in' acts as a link.
(Other definitions for befriend that I've seen before include "Look after" , "Bond with" , "Provide support as a chum" , "Become mates with" , "care for?" .)