Crossword Genius

Emphasising it's behaving badly (7,2)

Ross

I believe the answer is:

playing up

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'emphasising' is the definition.
Although both the answer and definition are present participle verbs, I cannot see how they can define each other.

'behaving badly' is the wordplay.
'behaving' becomes 'playing' (playing is a kind of behaving).
'badly' becomes 'up' (I can't justify this - if you can you should believe this answer much more).
'playing'+'up'='PLAYING UP'

'it's' is the link.

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I've seen this clue in the Evening Standard.
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