Fit again - that's a surprise (4,3)

I believe the answer is:

well now

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'a surprise' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'fit again' is the wordplay.
'fit' becomes 'well' (associated in meaning).
'again' becomes 'now' (I can't explain this - if you can you should give a lot more credence to this answer).
'well'+'now'='WELL NOW'

'that's' is the link.

Can you help me to learn more?

(Another definition for well now that I've seen is " Phrase to preface comments".)

I've seen this clue in The Independent.

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