To the west, a cool and a green Pacific region (7)
I believe the answer is:
oceania
'pacific region' is the definition.
(I've seen this before)
'to the west a cool and a green' is the wordplay.
'to the west' says the letters should be written backwards.
'cool' becomes 'in' (I've seen this in other clues**).
'and' says to put letters next to each other.
'green' becomes 'eco' (abbreviation for ecological).
'a'+'in'+'a'+'eco'='ainaeco'
'ainaeco' reversed gives 'OCEANIA'.
(Other definitions for oceania that I've seen before include "Pacific Ocean area" , "Islands of the central and South Pacific" , "Large South Pacific region" , "Pacific island area" , "Polynesia, Micronesia and Melanesia" .)