Crossword Genius

Upset cast cancelled rest (5,3,7)

Ross

I believe the answer is:

throw off balance

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

'upset' is the definition.
(thesaurus)

'cast cancelled rest' is the wordplay.
I cannot quite see how this works, but
'cast' could be 'throwoff' (synonyms) and 'throwoff' is found in the answer.
'rest' could be 'balance' (I've seen this before) and 'balance' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Daily Express.
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