Charlie, county member, entertained by adventurous girl assistant (10)
I believe the answer is:
accomplice
'assistant' is the definition.
(thesaurus)
'charlie county member entertained by adventurous girl' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'county' becomes 'co'.
'member' becomes 'MP' (Member of Parliament).
'entertained by' is an insertion indicator (inserted letters are hosted or entertained).
'adventurous girl' becomes 'Alice' (main character in Alice's Adventures in Wonderland).
'c'+'co'+'mp'='ccomp'
'ccomp' going within 'alice' is 'ACCOMPLICE'.
(Other definitions for accomplice that I've seen before include "Partner in crime" , "ally" , "criminal partner" , "Fellow criminal" , "Criminal's associate" .)