Compliant American chaps with expert (8)
I believe the answer is:
amenable
'compliant' is the definition.
(similar in meaning)
'american chaps with expert' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'chaps' becomes 'men' (chap means a man).
'with' is a charade indicator (letters next to each other).
'expert' becomes 'able' (able can mean expert or talented).
'a'+'men'+'able'='AMENABLE'
(Other definitions for amenable that I've seen before include "Willing to comply" , "likely to cooperate - with 3a" , "Flexible, agreeable" , "Willing to yield or be influenced" , "Easily persuaded or controlled" .)