High mountains (4)
I believe the answer is:
alps
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">high mountains</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for alps that I've seen before include "Mountain system, highest peak Mont Blanc" , "high points" , "Pals seen in mountains" , "Pals put on the mountains" , "With pals in great mountains" .)