Strive to replace the metal fasteners (6)
I believe the answer is:
rivets
'metal fasteners' is the definition.
(I've seen this in another clue)
'strive to replace' is the wordplay.
'to replace' indicates an anagram (I've seen 'replacing' mean this (placing again)).
'strive' anagrammed gives 'RIVETS'.
'the' acts as a link.
(Other definitions for rivets that I've seen before include "Metal pins or bolts for holding together two plates of metal" , "Steel pins holding metal sheets together" , "Short metal pins" , "Small pins for joining metal sheets" .)