Crossword Genius

The instruction to be economical is falling on deaf ears (7)

Ross

I believe the answer is:

useless

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'deaf ears' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?

I can't explain the remainder of the clue.

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(Other definitions for useless that I've seen before include "Counterproductive" , "Of no practical application, not worth keeping" , "idle" , "Worth zilch" , "Far from impressive" .)

I've seen this clue in the Evening Standard.
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