Jump on one leg (3)
I believe the answer is:
hop
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">jump on one leg</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 hop that I've seen before include "Jump; dance" , "Jump on a pogo stick" , "Climbing plant - jump!" , "Short trip" , "Skip; beer flavouring ingredient" .)