Mosquito stoppers (4)
I believe the answer is:
nets
'mosquito stoppers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nets that I've seen before include "Practice pitches (cricket)" , "Meshes to catch fish, say" , "Catches (fish)" , "Traps, to catch fish say" , "'Traps for 29 dn, say (4)'" .)