Polite, rattled, taking cross abuse (7)
I believe the answer is:
exploit
'abuse' is the definition.
(thesaurus)
'polite rattled taking cross' is the wordplay.
'rattled' indicates anagramming the letters.
'taking' means one lot of letters goes inside another.
'cross' becomes 'x'.
'polite' with letters rearranged gives 'eploit'.
'eploit' placed around 'x' is 'EXPLOIT'.
(Other definitions for exploit that I've seen before include "Take unfair advantage of" , "Heroic achievement" , "Adventure, bold or notable deed" , "Make good or selfish use of" , "put to good use" .)