Is rare rock from a range of mountains? (6)
I believe the answer is:
sierra
'a range of mountains?' is the definition.
(sierra is a kind of range of mountains)
'is rare rock' is the wordplay.
'rock' indicates an anagram.
'is'+'rare'='israre'
'israre' with letters rearranged gives 'SIERRA'.
'from' is the link.
(Other definitions for sierra that I've seen before include "that Romeo is not after" , "Model of car from Ford" , "Nato alphabet 'S'" , "International codeword" , "Long range" .)