Former Welsh rite given a new twist (9)
I believe the answer is:
erstwhile
'former' is the definition.
('erstwhile' can be a synonym of 'former')
'welsh rite given a new twist' is the wordplay.
'given a new twist' is an anagram indicator.
'welsh'+'rite'='welshrite'
'welshrite' with letters rearranged gives 'ERSTWHILE'.
(Other definitions for erstwhile that I've seen before include "Former, previous" , "Quondam" , "Former - list where (anag)" , "Formerly" , "In the past" .)