Merit of learning (4)
I believe the answer is:
earn
'merit' is the definition.
(I've seen this in other clues)
'of learning' is the wordplay.
'of' indicates the answer is hidden within the clue.
'EARN' is hidden in the letters of 'learning'.
(Other definitions for earn that I've seen before include "Gain, take in" , "Acquire money by labour" , "Receive by effort" , "Acquire by ones' effort" , "Acquire through merit" .)