Militant spoke outside clubs (7)
I believe the answer is:
radical
'militant' is the definition.
(I've seen this before)
'spoke outside clubs' is the wordplay.
'spoke' becomes 'radial' (I've seen this in other clues).
'outside' is an insertion indicator.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'radial' going around 'c' is 'RADICAL'.
(Other definitions for radical that I've seen before include "Extreme, ultra" , "Sweeping - reformer" , "Fundamental - non-conformist" , "stem" , "Politically extreme" .)