Honking (7)
I believe the answer is:
tooting
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">honking</span>' is the definition.<br/ ><span class="explanation-format__explanation">('toot' can be a synonym of 'honk')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tooting that I've seen before include "... what impatient motorist may be doing" , "somewhere in London?" , "Blowing" , "area south of Wandsworth" , "Showing impatience as driver" .)