No layman (3)
I believe the answer is:
pro
'no layman' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pro that I've seen before include "One doesn't play just for the love of it, in short" , "With qualifications" , "Golfer" , "In brief, he's no amateur" , "Paid worker" .)