Lens failed to improve abstinence (4-6)

I believe the answer is:

self-denial

'abstinence' is the definition.
(thesaurus)

'lens failed to improve' is the wordplay.
'to improve' indicates anagramming the letters.
'lens'+'failed'='lensfailed'
'lensfailed' anagrammed gives 'SELF-DENIAL'.

(Another definition for self-denial that I've seen is " Unwillingness to gratify one's own desires".)

I've seen this clue in The Daily Express.

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