Scat syllable (3)
I believe the answer is:
doo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">scat syllable</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for doo that I've seen before include "(see 16 across)" , "Scooby - - (cartoon)" , "Dove (Scottish)" .)