Return favour for rookie (4)
I believe the answer is:
noob
'rookie' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'return favour' is the wordplay.
'return' is a reversal indicator.
'favour' becomes 'boon' (I've seen this before).
'boon' backwards is 'NOOB'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for noob that I've seen before include "novice" , "inexperienced person" .)