Male sheep returns to ruin (3)
I believe the answer is:
mar
'ruin' is the definition.
(I've seen this before)
'male sheep returns' is the wordplay.
'male sheep' becomes 'ram' (a ram is a male sheep).
'returns' shows that the letters should be reversed in order.
'ram' backwards is 'MAR'.
'to' is the link.
(Other definitions for mar that I've seen before include "Oh dear!" , "Disfigure" , "Spoil or deface" , "A windy month" , "Blight" .)