In-form professional? (13)
I believe the answer is:
schoolteacher
'professional?' is the definition.
(schoolteacher is a kind of professional)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for schoolteacher that I've seen before include "Master, say" , "Instructor" , "tutor" , "Chips perhaps" , "who has class?" .)