Stray sheep going round the circuit (4)
I believe the answer is:
roam
'stray' is the definition.
(I know that stray can be written as roam)
'sheep going round the circuit' is the wordplay.
'sheep' becomes 'ram' (male sheep).
'going round' indicates putting letters inside (some letters go around others).
'the circuit' becomes 'o'.
'ram' enclosing 'o' is 'ROAM'.
(Other definitions for roam that I've seen before include "go on walkabout" , "Peregrinate" , "Prowl" , "Wander widely" , "'Wander, ramble (4)'" .)