Ultimate catch (3)
I believe the answer is:
net
This clue is a double definition.
'ultimate' is the first definition.
(as in final or ultimate profits)
'catch' is the second definition.
(net can mean to catch)
(Other definitions for net that I've seen before include "What separates court opponents" , "Trap; open-weave fabric" , "Mesh; after tax" , "Tennis equipment" , "Meshwork" .)