Lean against for balance (4)

I believe the answer is:

rest

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'lean' is the definition.
(I've seen this before)

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

(Other definitions for rest that I've seen before include "Tranquillity" , "'Relax, pause from work (4)'" , "Holiday" , "Lie down" , "Settle" .)

I've seen this clue in the Evening Standard.

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