Dog of mixed breed (7)
I believe the answer is:
mongrel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dog of mixed breed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for mongrel that I've seen before include "mixed stock" , "Cross" , "of mixed blood" , "Dog of mixed breed" , "Mixed-breed dog" .)