Rock's ___ Leppard (3)
I believe the answer is:
def
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rock's leppard</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for def that I've seen before include "explanation" , "Brilliant" , "Quick and skilful." .)