Non-professional set (3)
I believe the answer is:
lay
I believe this clue is a double definition.
'non-professional' is the first definition.
(as in a layman)
'set' is the second definition.
(both can mean to place something)
(Other definitions for lay that I've seen before include "Place (bet)" , "Song-ballad" , "Put down (in position)" , "Non-professional - ballad" , "Air" .)