European mountains (4)
I believe the answer is:
alps
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">european mountains</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 alps that I've seen before include "Mountains in Central Europe" , "high points" , "European mountains" , "Eur. mountain range" , "Slap about in mountains" .)