Junkyard dog
I believe the answer is:
cur
'junkyard dog' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cur that I've seen before include "Mongrel - coward" , "Base fellow" , "Inferior dog or one of mixed breed" , "Scoundrel; mongrel dog" , "Surly dog (or person)" .)