Previously unknown (7-2)
I believe the answer is:
unheard-of
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">previously unknown</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 unheard-of that I've seen before include "Previously unknown" , "Without precedent" , "Not previously known or done - inaudible?" , "Unknown - novel" , "Fear hound being not previously known" .)