Monkeys with dirty child not right wearing hats (9)
I believe the answer is:
capuchins
'monkeys' is the definition.
(capuchin is a kind of monkey)
'dirty child not right wearing hats' is the wordplay.
'dirty child' becomes 'urchin' (an urchin is a poor or dirty child).
'not' is a deletion indicator.
'right' becomes 'r' (common abbreviation).
'wearing' is an insertion indicator.
'hats' becomes 'caps' (cap is a type of hat).
'urchin' with 'r' taken out is 'uchin'.
'uchin' inserted inside 'caps' is 'CAPUCHINS'.
'with' acts as a link.
(Other definitions for capuchins that I've seen before include "Primates" , "some in Franciscan order" , "China cups for friars or monkeys" .)