A new setter, I state, is heavenly (9)
I believe the answer is:
angelical
'heavenly' is the definition.
(I've seen this before)
'a new setter i state' is the wordplay.
'a' becomes 'an'.
'new setter' becomes 'gel' (something which sets. I am not sure about the 'new' bit.).
'state' becomes 'cal' (short for California).
'an'+'gel'+'i'+'cal'='ANGELICAL'
'is' acts as a link.
(Other definitions for angelical that I've seen before include "Exceptionally beautiful" , "sublime innocence" , "heavenly" .)