Bird ran wild in arena (4,3)
I believe the answer is:
barn owl
'bird' is the definition.
(barn owl is a kind of bird)
'ran wild in arena' is the wordplay.
'wild' indicates anagramming the letters.
'in' means one lot of letters goes inside another.
'arena' becomes 'bowl' ('bowl' can be a synonym of 'arena').
'ran' with letters rearranged gives 'arn'.
'arn' going within 'bowl' is 'BARN OWL'.
(Other definitions for barn owl that I've seen before include "Endangered night bird" , "Large hunting bird" , "Countryside bird" , "Large bird of prey" , "Night-flying raptor" .)