Incisive Tory, oddly with charm (9)
I believe the answer is:
trenchant
'incisive' is the definition.
(thesaurus)
'tory oddly with charm' is the wordplay.
'oddly' means one should take alternating letters.
'with' is a charade indicator (letters next to each other).
'charm' becomes 'enchant' ('enchant' can be a synonym of 'charm'**).
The alternating letters of 'tory' are 'tr'.
'tr'+'enchant'='TRENCHANT'
(Other definitions for trenchant that I've seen before include "Incisive in style" , "Showing keenness" , "Vigorous, incisive" , "Clear-cut and hard-hitting" , "Keen" .)