Crossword Genius

Cut back duty originally capped by fuel regulator (9)

Ross

I believe the answer is:

throttled

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'capped by fuel regulator' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Maybe there's an association between them I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for throttled that I've seen before include "Suppressed" , "Choked" , "Strangled manually" .)

I've seen this clue in The Independent.
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