Trap; after tax (3)
I believe the answer is:
net
This clue is a double definition.
'trap' is the first definition.
(I know that net is a type of trap)
'after tax' is the second definition.
(I've seen this in another clue)
(Other definitions for net that I've seen before include "Mesh or web" , "Clear profit or gain" , "Mesh; after tax" , "catch fish" , "difficulty" .)