Man sends back unused ring? (4)
I believe the answer is:
owen
'man' is the definition.
'back unused ring?' is the wordplay.
'back' is a reversal indicator.
'unused' becomes 'new' (similar in meaning).
'ring?' becomes 'o' (O is the shape of a ring).
'new'+'o'='newo'
'newo' in reverse letter order is 'OWEN'.
'sends' is the link.
(Other definitions for owen that I've seen before include "Wilfred - - , WW1 poet" , "'E won over the Welshman" , "Clive --, English actor" , "Welsh industrialist and social reformer, founder of cooperative communities, d. 1858" , "Wilfred - - , WWI poet" .)