Promise to train sportsman, maybe (7)
I believe the answer is:
semipro
'sportsman maybe' is the definition.
'promise to train' is the wordplay.
'to train' indicates anagramming the letters (to train can mean to grow something into a shape).
'promise' is an anagram of 'SEMIPRO'.
(Other definitions for semipro that I've seen before include "part-timer" , "he may take part for money" , "One not giving up the day job" .)