He's not a star but more (5)
I believe the answer is:
extra
'more' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for extra that I've seen before include "E.g. wide in cricket" , "Auxiliary" , "23 player?" , "person in shot?" , "more than required" .)