Extremist caught in awful tragedy (5)
I believe the answer is:
ultra
'extremist' is the definition.
('ultra' can be a synonym of 'extremist')
'caught in awful tragedy' is the wordplay.
'caught in' says the answer is hidden in the clue.
'ULTRA' is hidden within 'awful tragedy'.
(Other definitions for ultra that I've seen before include "holding extreme position" , "Person holding extreme views" , "extreme measures" , "(One who is) extreme (in eg political opinion)" , "Prefix meaning beyond or excessively" .)