Locks seat when Charlie leaves (4)

I believe the answer is:

hair

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'locks' is the definition.
(locks can mean hair)

I don't understand the remainder of the clue.

(Other definitions for hair that I've seen before include "Bristle" , "Human head covering" , "It grows from a follicle" , "Outgrowth from the skin" , "It grows from the skin" .)

I've seen this clue in the Sydney Morning Herald.

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