Bird dog with no lead (5)
I believe the answer is:
eagle
'bird' is the definition.
(eagle is a kind of bird)
'dog with no lead' is the wordplay.
'dog' becomes 'beagle' (beagle is a kind of dog).
'with no lead' means to remove the first letter.
'beagle' with its first letter taken away is 'EAGLE'.
(Other definitions for eagle that I've seen before include "drugs with silver left inside" , "Flyer" , "Bird of prey, may be golden" , "Bird of prey; former children's comic" , "High-flyer" .)