Good beam for hard worker (7)
I believe the answer is:
grafter
'hard worker' is the definition.
(I've seen this before)
'good beam' is the wordplay.
'good' becomes 'g' (abbreviation).
'beam' becomes 'rafter' (rafter is a kind of beam).
'g'+'rafter'='GRAFTER'
'for' acts as a link.
(Other definitions for grafter that I've seen before include "Hard worker - corrupt operator" , "One who works hard" .)