Crossword Genius

With ferocity and force (5,3,4)

Ross

I believe the answer is:

tooth and nail

(Other definitions for tooth and nail that I've seen before include "With all possible vigour" , "Fiercely" , "(Fight) without restraint" , "With the utmost vigour" , "With greatest vigour" .)

I've seen this clue in The Independent.
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