Tuna catcher (3)
I believe the answer is:
net
'tuna catcher' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for net that I've seen before include "Mesh; entrap" , "Open weave fabric" , "What separates court opponents" , "Tennis court feature" , "Catch -- after all deductions" .)