Perforce, thoroughly fulfil Baker’s role in audition (9)

I believe the answer is:

needfully

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'fulfil baker's role in audition' is the definition.
I can't tell whether this definition defines the answer.

'perforce thoroughly' is the wordplay.
'perforce' becomes 'need' (I can't explain this - if you can you should believe this answer much more).
'thoroughly' becomes 'fully' (I've seen this in another clue).
'need'+'fully'='NEEDFULLY'

Can you help me to learn more?

(Another definition for needfully that I've seen is " Necessarily".)

I've seen this clue in The Times.

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