Composer in a happy state (5)
I believe the answer is:
bliss
This could be a double definition.
'composer' is the first definition.
(British composer Arthur Bliss)
'happy state' is the second definition.
'bliss' can be an answer for 'state' (bliss is a kind of state). I'm unsure of the 'happy' bit.
'in a' acts as a link.
Can you help me to learn more?
(Other definitions for bliss that I've seen before include "Cloud nine" , "of composing?" , "Sir Arthur --, British composer" , "Highest happiness" , "Great happiness" .)