Shock at being almost bitten? (4)
I believe the answer is:
stun
'shock' is the definition.
('stun' can be a synonym of 'shock')
'being almost bitten?' is the wordplay.
'being almost' means to remove the last letter (most of the word but not all of it).
'bitten?' becomes 'stung' ('sting' can be a synonym of 'bite').
'stung' with its final letter removed is 'STUN'.
'at' acts as a link.
(Other definitions for stun that I've seen before include "Daze, knock senseless" , "Shock, flabbergast" , "Surprise greatly, knock someone''s socks off" , "Knock cold" , "Knock into a semi-conscious state" .)