Discourage careful eater, initially itching to quit (5)

I believe the answer is:

deter

'discourage' is the definition.
(I know that discourage can be written as deter)

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

(Other definitions for deter that I've seen before include "Discourage, put off" , "Inhibit" , "'Discourage, dissuade (5)'" , "Hinder, prevent" , "Hinder, discourage" .)

I've seen this clue in The Times.

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