Polo mount (4)
I believe the answer is:
pony
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">polo mount</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 pony that I've seen before include "staked 25" , "Small horse - GBP25" , "Small breed of horse" , "Sum of 25 (Informal)" , "Animal; PS25" .)