A pony's transformed with lei - in this Pacific region? (9)
I believe the answer is:
'this pacific region?' is the definition.
(I've seen this before)
'a pony's transformed with lei' is the wordplay.
'transformed with' indicates an anagram.
'aponys' anagrammed with 'lei' makes 'POLYNESIA'.
'in' is the link.
(Other definitions for polynesia that I've seen before include "large group of islands" , "Extensive group of Pacific islands" , "Pacific region?" , "Islands including Hawaii, Tonga, Samoa, etc." , "Pacific islands incl. N Zealand, Samoa and Hawaii" .)