Big punch up, say, ruined sanctions (5)

I believe the answer is:

okays

I'm a little stuck... Click here to teach me more about this clue!

'sanctions' is the definition.
(I know this)

'big punch up say ruined' is the wordplay.
'big punch' becomes 'ko' (KO punch is an example. I am not sure about the 'big' bit.).
'up' is a reversal indicator (in down clue: letters go upwards).
'ruined' indicates an anagram.
'ko' reversed gives 'ok'.
'say' anagrammed gives 'ays'.
'ok'+'ays'='OKAYS'

Can you help me to learn more?

(Other definitions for okays that I've seen before include "Sanctions" , "Authorises" , "Gives the go-ahead" , "Agrees" , "Gives the thumbs up" .)

I've seen this clue in the Sydney Morning Herald.

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