In computing, abbreviation can be a trap (3)
I believe the answer is:
net
'trap' is the definition.
(net is a type of trap)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for net that I've seen before include "Catch -- after all deductions" , "Mesh; after tax" , "Meshed trap" , "Fish-catching mesh" , "Mesh; entrap" .)