It's perfectly fine to use bazooka, now and then (3)

I believe the answer is:

aok

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'it's perfectly fine' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'bazooka now and then' is the wordplay.
'now and then' indicates alternate letters (letters taken on a regular basis, now and then).
The alternate letters of 'bazooka' are 'AOK'.

'to use' is the link.

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I've seen this clue in The Irish Times.

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