Sport losing wife's attention (3)
I believe the answer is:
ear
'attention' is the definition.
(ear is a kind of attention)
'sport losing wife's' is the wordplay.
'sport' becomes 'wear' (I've seen this before).
'losing' suggests deleting specific letters.
'wife' becomes 'w'.
'wear' with 'w' taken away is 'EAR'.
(Other definitions for ear that I've seen before include "Musical ability" , "Aural organ" , "Seed-bearing spike" , "Lend one and listen" , "Speculator ignoring British" .)