Not dangerous to wave to criminal (4,7)

I believe the answer is:

safe breaker

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'criminal' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?

'not dangerous to wave' is the wordplay.
'not dangerous' becomes 'safe' ('safe' is the opposite to 'dangerous').
'to wave' becomes 'breaker' (breaker is a kind of wave).
'safe'+'breaker'='SAFE-BREAKER'

'to' is the link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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