Old servant disturbing a hidden man (10)

I believe the answer is:

handmaiden

I'm a little stuck... Click here to teach me more about this clue!

'old servant' is the definition.
'handmaiden' can be an answer for 'servant' (handmaiden is a kind of servant). I am not sure about the 'old' bit.

'disturbing a hidden man' is the wordplay.
'disturbing' indicates anagramming the letters (I've seen this in other clues).
'a'+'hidden'+'man'='ahiddenman'
'ahiddenman' with letters rearranged gives 'HANDMAIDEN'.

Can you help me to learn more?

(Another definition for handmaiden that I've seen is " Female servant".)

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