Trojan worker provides good support (7)
I believe the answer is:
grafter
'trojan worker' is the definition.
(trojan can mean a hard worker or grafter)
'good support' is the wordplay.
'good' becomes 'g' (abbreviation).
'support' becomes 'rafter' (architectural support).
'g'+'rafter'='GRAFTER'
'provides' is the link.
(Other definitions for grafter that I've seen before include "One who works hard" , "Hard worker - corrupt operator" .)