The Danes' mountains? (5)
I believe the answer is:
andes
'mountains?' is the definition.
(I've seen this before)
'the danes'' is the wordplay.
'danes' anagrams to 'ANDES'.
Though, I'm not clear how this is indicated.
Can you help me to learn more?
(Other definitions for andes that I've seen before include "Danes in S American mountains" , "A geographical feature" , "Mountains in west" , "Danes seen in mountains" , "danes found in mountains" .)