Extremist in Kabul traced (5)
I believe the answer is:
ultra
'extremist' is the definition.
(ultra can mean an extremist or radical)
'in kabul traced' is the wordplay.
'in' indicates a hidden word.
'ULTRA' is hidden in the letters of 'kabul traced'.
(Other definitions for ultra that I've seen before include "Fanatic" , "lacking moderation" , "Above, beyond, super" , "Prefix meaning excessively or extremely" , "Project started at Bletchley Park in 1939 to break the Enigma code" .)