Vicar’s average child (6)
I believe the answer is:
parson
'vicar's' is the definition.
(both are members of the clergy)
'average child' is the wordplay.
'average' becomes 'par' (average score in golf).
'child' becomes 'son' (male child).
'par'+'son'='PARSON'
(Other definitions for parson that I've seen before include "Churchman" , "Aprons (anag.)" , "A rector or vicar" , "service provider" , "man of the church" .)