Shock caused by dangerous feat? No end (4)
I believe the answer is:
stun
'shock' is the definition.
('stun' can be a synonym of 'shock')
'dangerous feat? no end' is the wordplay.
'dangerous feat?' becomes 'stunt' (I've seen this before).
'no end' means to remove the last letter.
'stunt' with its final letter taken off is 'STUN'.
'caused by' is the link.
(Other definitions for stun that I've seen before include "floor" , "Render semi-conscious with blow" , "Render unconscious" , "Stupefy - daze" , "Daze or bewilder" .)