Return of people keeping dry around cool, green region (7)
I believe the answer is:
oceania
'region' is the definition.
(region of Earth)
'return of people keeping dry around cool green' is the wordplay.
'return of' shows that the letters should be reversed in order.
'people keeping dry' becomes 'AA' (Alcoholics Anonymous - 'dry' as in not drinking).
'around' indicates putting letters inside.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'green' becomes 'eco' (abbreviation for ecological).
'aa' enclosing 'in' is 'aina'.
'aina'+'eco'='ainaeco'
'ainaeco' back-to-front is 'OCEANIA'.
(Other definitions for oceania that I've seen before include "Islands of Pacific and adjacent seas" , "Pacific island area" , "The Pacific islands taken together" , "Pacific Ocean area" , "Islands of the central and South Pacific" .)