Amateur film gripping quiet child (9)
I believe the answer is:
layperson
'amateur' is the definition.
(I've seen this before)
'film gripping quiet child' is the wordplay.
'film' becomes 'layer' (film can mean a thin layer of something).
'gripping' is an insertion indicator (inserted letters are gripped).
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'child' becomes 'son' (male child).
'layer' placed around 'p' is 'layper'.
'layper'+'son'='LAYPERSON'
(Other definitions for layperson that I've seen before include "Non-specialist" , "one of his flock maybe" , "parishioner?" , "Not an expert" , "Amateur" .)