Inflexible ideologue (9)
I believe the answer is:
hardliner
'inflexible ideologue' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hardliner that I've seen before include "Inflexible ideologue" , "Resolute advocate" , "dogmatic type" , "Doctrinaire type" , "One pursuing an uncompromising policy" .)