Merit student goes before master (5)
I believe the answer is:
learn
'master' is the definition.
(I've seen this before)
'merit student goes before' is the wordplay.
'merit' becomes 'earn' (I've seen this before).
'student goes' becomes 'l' (I can't explain this - if you can you should give a lot more credence to this answer).
'before' means one lot of letters go next to another.
'earn' put after 'l' is 'LEARN'.
Can you help me to learn more?
(Other definitions for learn that I've seen before include "Find out - assimilate facts" , "Take in" , "Discover - study" , "Master" , "Gain knowledge or skills" .)