Rein for rover (5)
I believe the answer is:
leash
'rein for rover' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for leash that I've seen before include "Rope used to restrain an animal" , "Animal restraint" , "Strap for holding a dog while walking" , "Bind" , "Restraint for a dog" .)