Put down crew as non-professional (6)
I believe the answer is:
layman
'non-professional' is the definition.
(I've seen this before)
'put down crew' is the wordplay.
'put down' becomes 'lay' ('lay' can be a synonym of 'put down'**).
'crew' becomes 'man' (I've seen this before).
'lay'+'man'='LAYMAN'
'as' acts as a link.
(Other definitions for layman that I've seen before include "He's not a priest or specialist" , "He's not military or clerical" , "Non-professional male" , "He's not clergy or military" , "Someone who is not an expert" .)