Crossword Genius

Fierce blow to give ace (5-3-4)

Ross

I believe the answer is:

tooth-and-nail

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

'fierce blow to give ace' is the definition.
I can't judge whether this definition defines the answer.

'blow to give ace' is the wordplay.
I cannot really understand how this works, but
'blow' could be 'toot' (I've seen this in another clue) and 'toot' is located in the answer.
'give' could be 'hand' (synonyms) and 'hand' is located in the answer.
'ace' could be 'nail' (I've seen this in another clue) and 'nail' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.
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