Waste of resources potentially nice? Nice and iffy (12)

I believe the answer is:

inefficiency

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'waste of resources' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'potentially nice? nice and iffy' is the wordplay.
'potentially' indicates anagramming the letters (letters have the potential to spell a new word).
'and' is a charade indicator (letters next to each other).
'nice'+'nice'='nicenice'
'nicenice' after 'iffy' is 'iffynicenice'.
'iffynicenice' with letters rearranged gives 'INEFFICIENCY'.

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I've seen this clue in The Times.

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