Blab about (4,2)
I believe the answer is:
tell on
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blab about</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 tell on that I've seen before include "Betray (informal)" , "Give away secrets" .)