Sturdy canine (7)
I believe the answer is:
bulldog
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sturdy canine</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for bulldog that I've seen before include "Breed of canine; stationery clip" , "Tenacious person - sturdy canine" , "Thematic type [DOG]" , "Sturdy British canine" , "Tenacious animal" .)