Fervent or militant proponents (7)
I believe the answer is:
zealots
'fervent or militant proponents' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for zealots that I've seen before include "Partisans" , "Extremists" , "Gung-ho types" , "Fervent or militant proponents" , "Extreme enthusiasts" .)