Violent prick going quiet to loud (6)

I believe the answer is:

fierce

'violent' is the definition.
(similar in meaning)

I don't understand the rest of the clue.

(Other definitions for fierce that I've seen before include "Violent in temper or manner" , "Aggressive; intense" , "Savage - vehement" , "Violent and aggressive" , "Violent in temper, not gentle" .)

I've seen this clue in The Guardian.

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