Resin needs to be firm, mate (5)
I believe the answer is:
copal
'resin' is the definition.
(I've seen this before)
'to be firm mate' is the wordplay.
'to be firm' becomes 'co' (a firm is a company).
'mate' becomes 'pal' (I've seen this before**).
'co'+'pal'='COPAL'
'needs' is the link.
(Other definitions for copal that I've seen before include "Aromatic tree resin" , "Resin used in varnish" , "Hard resin" .)