Crossword Genius

It’s probably hearts she breaks! (7)

Ross

I believe the answer is:

smasher

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

'it's probably hearts' is the definition.
I can't tell whether this defines the answer.

'she breaks' is the wordplay.
I cannot quite understand how this works, but
'she' could be 'sher' and 'sher' is found within the answer.
The remaining letters 'sma' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for smasher that I've seen before include "an attacking tennis player?" , "who is attractive to men?" , "responsible for break-up?" , "Wonderful thing" , "Pretty woman" .)

I've seen this clue in the Evening Standard.
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