Catch in one trap (3)
I believe the answer is:
net
'catch' is the definition.
(net can mean to catch)
'in one trap' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NET' is hidden within 'one trap'.
(Other definitions for net that I've seen before include "device to divide the court" , "Lattice" , "Fish-catching mesh" , "Overall; mesh" , "Clear profit or gain" .)