Insects more dangerous when beheaded (5)
I believe the answer is:
wasps
'insects' is the definition.
(wasp is a kind of insect)
'more dangerous when beheaded' is the wordplay.
I cannot really see how this works, but
'when' could be 'as' (eg 'when I walked' means 'as I walked') and 'as' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for wasps that I've seen before include "Rugby club" , "Members of rugby team" , "English Protestant stingers?" , "Striped stinging insects" , "Stinging hymenopterans" .)