Prize winner, finally official (9)

I believe the answer is:

treasurer

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'official' is the definition.
(I've seen this before)

'prize winner finally' is the wordplay.
'prize' becomes 'treasure' (synonyms).
'winner finally' becomes 'r' (I am not sure about this - if you are sure you should believe this answer much more).
'treasure'+'r'='TREASURER'

Can you help me to learn more?

(Other definitions for treasurer that I've seen before include "Financial administrator" , "One of main officers of a society" , "one safeguarding funds" , "Person holding purse" , "Club official" .)

I've seen this clue in The Sunday Times and The Times.

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