Mixed metaphors involving Earth's climate (10)
I believe the answer is:
atmosphere
'climate' is the definition.
(atmosphere is a kind of climate)
'mixed metaphors involving earth's' is the wordplay.
'mixed' is an anagram indicator.
'involving' means one lot of letters goes inside another.
'earth' becomes 'E'.
'metaphors' with letters rearranged gives 'atmosphre'.
'atmosphre' placed around 'e' is 'ATMOSPHERE'.
(Other definitions for atmosphere that I've seen before include "character" , "Feel" , "We are always enveloped in this" , "Surrounding ambience" , "Feeling" .)