Insect or white-headed snake (4)

I believe the answer is:

wasp

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'insect' is the definition.
(I know that wasp is a type of insect)

'white-headed snake' is the wordplay.
'white' becomes 'w'.
'headed snake' becomes 'asp' (asp is a kind of snake. I am not sure about the 'headed' bit.).
'w'+'asp'='WASP'

'or' is the link.

Can you help me to learn more?

(Other definitions for wasp that I've seen before include "Stingy type" , "spiteful person?" , "Middle class American" , "Sort of privileged American" , "A hymenopteran" .)

I've seen this clue in the Evening Standard.

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