Snakes and insects beheaded (4)
I believe the answer is:
asps
'snakes' is the definition.
(asp is a kind of snake)
'insects beheaded' is the wordplay.
'insects' becomes 'wasps' (wasp is a kind of insect).
'beheaded' means to remove the first letter (the head of the word is removed).
'wasps' with its initial letter taken off is 'ASPS'.
'and' is the link.
(Other definitions for asps that I've seen before include "Poisonous creatures" , "Pass (anag)" , "Pass among snakes" , "Deadly snakes" , "because of their venom?" .)