Some of the rarest artworks begin again! (7)
I believe the answer is:
restart
'begin again' is the definition.
('start' can be a synonym for 'begin' so perhaps 'restart' is OK for 'begin again')
'some of the rarest artworks' is the wordplay.
'some of' indicates a hidden word.
'RESTART' is hidden in the letters of 'rarest artworks'.
(Other definitions for restart that I've seen before include "Jumping the gun will mean" , "launch again" , "begin afresh" , "Resume" , "Begin anew" .)