Driving back 45 inches a long time ago in regret (9)

I believe the answer is:

repellent

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'driving back 45 inches a long time' is the definition.
I can't tell whether this defines the answer.

'ago in regret' is the wordplay.
'ago' becomes 'ell' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'regret' becomes 'repent' (synonyms).
'ell' placed into 'repent' is 'REPELLENT'.

Can you help me to learn more?

(Other definitions for repellent that I've seen before include "Obnoxious" , "Hideous" , "Repugnant, loathsome" , "Arousing distaste or not penetrable" , "Causing distaste" .)

I've seen this clue in The Guardian.

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