Locks personnel department with robot inside (4)

I believe the answer is:

hair

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

'personnel department with robot inside' is the wordplay.
'personnel department' becomes 'HR' (Human Resources).
'with' is an insertion indicator.
'robot inside' becomes 'ai' (I can't justify this - if you can you should believe this answer much more).
'hr' going around 'ai' is 'HAIR'.

Can you help me to learn more?

(Other definitions for hair that I've seen before include "Musical - locks" , "Thread-like structure(s)" , "Red face powder" , "shock" , "Tresses" .)

I've seen this clue in The Mirror.

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