Everlasting variety for Peter and Paul (9)
I believe the answer is:
perpetual
'everlasting' is the definition.
(I know that everlasting can be written as perpetual)
'variety for peter and paul' is the wordplay.
'variety for' is an anagram indicator.
'and' says to put letters next to each other.
'peter' after 'paul' is 'paulpeter'.
'paulpeter' with letters rearranged gives 'PERPETUAL'.
(Other definitions for perpetual that I've seen before include "Endless, lasting" , "Going on for ever" , "Nonstop" , "Going on forever" , "Perennial" .)