A dreadful barber’s not in agreement (2,4)

I believe the answer is:

at odds

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'not in agreement' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for at odds that I've seen before include "In disagreement or conflict - like bookies?" , "In conflict with, oppposed to (2,4)" , "Conflicting (with)" , "Opposed, in conflict with" , "Quarrelling" .)

I've seen this clue in The Times.

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