Total number sent back (3)
I believe the answer is:
net
'total' is the definition.
(I've seen this in another clue)
'number sent back' is the wordplay.
'number' becomes 'ten' (ten is a kind of whole number).
'sent back' is a reversal indicator.
'ten' written backwards gives 'NET'.
(Other definitions for net that I've seen before include "Open-meshed fabric" , "catch fish" , "land" , "Fine open-weave fabric" , "Open-mesh material" .)