Once a very bad pennyworth? (8)

I believe the answer is:

dreadful

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'bad pennyworth?' is the definition.
'dreadful' can be an answer for 'bad' (thesaurus). I'm not sure about the 'pennyworth?' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for dreadful that I've seen before include "Shockingly bad" , "Extremely bad or disagreeable" , "Atrocious, awful" , "Informally very bad, perhaps the weather" , "Dire, alarming" .)

I've seen this clue in the Evening Standard.

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