Layabout seen in bridle road (5)
I believe the answer is:
idler
'layabout' is the definition.
('idler' can be a synonym of 'layabout')
'in bridle road' is the wordplay.
'in' indicates a hidden word.
'IDLER' is hidden in the letters of 'bridle road'.
'seen' is the link.
(Other definitions for idler that I've seen before include "papers" , "Lollard" , "Someone unemployed" , "Lazybones; gear wheel" , "Drone" .)