Catch a number returning (3)
I believe the answer is:
net
'catch' is the definition.
(netting is a kind of catching)
'a number returning' is the wordplay.
'a number' becomes 'ten' (ten is a kind of number).
'returning' says the letters should be written in reverse.
'ten' back-to-front is 'NET'.
(Other definitions for net that I've seen before include "Snare or trap" , "It turns in every direction" , "Meshed trap" , "What separates court opponents" , "Trap made from mesh" .)