Eastern sierra -- wild scene for nature (7)
I believe the answer is:
essence
'for nature' is the definition.
(I've seen this before)
'eastern sierra wild scene' is the wordplay.
'eastern' becomes 'e'.
'sierra' becomes 'S' (phonetic alphabet: alpha, bravo, charlie etc.).
'wild' indicates an anagram.
'scene' with letters rearranged gives 'sence'.
'e'+'s'+'sence'='ESSENCE'
(Other definitions for essence that I've seen before include "Core, most vital part" , "required property" , "one of 21 [HEARTS]" , "Distinctive inner nature of person or thing" , "Flavour, spirit" .)