Good considerable number work hard (5)
I believe the answer is:
graft
'work hard' is the definition.
'graft' can be an answer for 'work' (I have seen 'Hard work' mean 'graft' so perhaps 'work' could also mean 'graft'). I'm not sure about the 'hard' bit.
'good considerable number' is the wordplay.
'good' becomes 'g' (abbreviation).
'considerable number' becomes 'raft' (I am not sure about this - if you are sure you should believe this answer much more).
'g'+'raft'='GRAFT'
Can you help me to learn more?
(Other definitions for graft that I've seen before include "Transfer of tissue - hard work!" , "Shoot; hard work" , "Hard work - corrupt profit" , "Transplant - hard work" , "Hard work - illicit gain" .)