Shock as attacked by insect? Not good! (4)
I believe the answer is:
stun
'shock' is the definition.
(both can mean to surprise)
'attacked by insect? not good' is the wordplay.
'attacked by insect?' becomes 'stung' (eg stung by a bee).
'not' indicates named letters should be taken away.
'good' becomes 'g' (abbreviation).
'stung' with 'g' taken out is 'STUN'.
'as' is the link.
(Other definitions for stun that I've seen before include "Anaesthetise" , "Daze or bewilder" , "Daze with nuts" , "Knock out temporarily" , "Daze, paralyse" .)