Holm oak (4)
I believe the answer is:
ilex
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">holm oak</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 ilex that I've seen before include "'Tree group, includes holly (4)'" , "Holly, classically" , "Holly, perhaps" , "Genus of trees that includes hollies" , "The holm-oak" .)