Blatant lie (7)
I believe the answer is:
whopper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blatant lie</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 whopper that I've seen before include "Blatant lie" , "A great big lie - or fish" , "Huge one; lie" , "Enormous lie" , "that 13 [TRUTH SERUM] might detect?" .)