Buff cast vetoed coda for once (7)
I believe the answer is:
devotee
'buff' is the definition.
(I know that buff can be written as devotee)
'cast vetoed coda for once' is the wordplay.
I cannot really understand how this works, but
an anagram of 'vetoed' is 'devote' which is located in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for devotee that I've seen before include "Big fan" , "Zealous follower" , "Great fan" , "A very loyal or loving person" , "dedicated person" .)