Crossword Genius

You change your attitude when you turn over this (1,3,4)

Ross

I believe the answer is:

a new leaf

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

'you change your attitude when you' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'turn over this' is the wordplay.
I cannot really understand how this works, but
'turn' could be 'leaf' (leafing is a kind of turning) and 'leaf' is located in the answer.
The remaining letters 'anew' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Hindu.
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