Sturdy trees (4)

I believe the answer is:
oaks
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sturdy trees</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 oaks that I've seen before include "Acorn producers" , "Soak up with trees" , "Epsom Classic race" , "Horse race - trees" , "Hardwood trees" .)