Power converted easily on islands (9)
I believe the answer is:
polynesia
'islands' is the definition.
(I've seen this before)
'power converted easily on' is the wordplay.
'power' becomes 'p' (symbol in physics).
'converted' indicates anagramming the letters.
'easily'+'on'='easilyon'
'easilyon' is an anagram of 'olynesia'.
'p'+'olynesia'='POLYNESIA'
(Other definitions for polynesia that I've seen before include "Antipodeans around here" , "The islands of eastern Oceania" , "Extensive group of Pacific islands" , "Pacific island group" , "Pacific islands incl. N Zealand, Samoa and Hawaii" .)