Web, for a fly (5)
I believe the answer is:
snare
I believe this clue is a double definition.
'web' is the first definition.
(I've seen this in another clue)
'for a fly' is the second definition.
(thesaurus)
(Other definitions for snare that I've seen before include "Trap or entangle" , "Kind of trap, often with noose" , "Loop of wire as trap" , "Pitfall" , "Entrap" .)