Dog slipping lead finds bird (5)
I believe the answer is:
eagle
'bird' is the definition.
(eagle is a type of bird)
'dog slipping lead' is the wordplay.
'dog' becomes 'beagle' (beagle is a kind of dog).
'slipping lead' means to remove the first letter (I've seen 'slips lead' mean this).
'beagle' with its initial letter taken away is 'EAGLE'.
'finds' acts as a link.
(Other definitions for eagle that I've seen before include "Symbolic American bird" , "five buck bit, or more" , "Bird of prey, may be golden" , "ten-dollar coin" , "experts are putting more than albatross?" .)