Is rare cuckoo 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 cuckoo' is the wordplay.
'cuckoo' indicates an anagram.
'is'+'rare'='israre'
'israre' is an anagram of 'SIERRA'.
'from' is the link.
(Other definitions for sierra that I've seen before include "International codeword" , "------ Nevada, mountains of Spain and California" , "Spanish range of mountains" , "A Spanish chain of mountains" , "mountain area" .)