Extremist drawing back after cult's uncovered (5)
I believe the answer is:
ultra
'extremist' is the definition.
(ultra can mean an extremist or radical)
'drawing back after cult's uncovered' is the wordplay.
'drawing' becomes 'art' (I've seen this before).
'back' shows that the letters should be reversed in order.
'after' says to put letters next to each other.
'uncovered' indicates the central letters.
The central letters of 'cult' are 'ul'.
'art' reversed gives 'tra'.
'tra' after 'ul' is 'ULTRA'.
(Other definitions for ultra that I've seen before include "Over the top" , "Extremely; an extremist" , "Immoderate" , "Project started at Bletchley Park in 1939 to break the Enigma code" , "lacking moderation" .)