Though ultra-efficient, can be bettered (9)

I believe the answer is:

superable

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'bettered' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives occasionally mean the same thing.

'though ultra-efficient' is the wordplay.
'though ultra' becomes 'super' (I can't explain this - if you can you should believe this answer much more).
'efficient' becomes 'able' (I've seen this before).
'super'+'able'='SUPERABLE'

'can be' is the link.

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I've seen this clue in the Evening Standard.

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