Nanny's nanny? (8)

I believe the answer is:

goatherd

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'nanny's nanny?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'nanny's nanny?' is the wordplay.
'nanny' becomes 'goat' (nanny is a female goat).
'nanny?' becomes 'herd' (I can't justify this - if you can you should believe this answer much more).
'goat'+'herd'='GOATHERD'

Can you help me to learn more?

(Other definitions for goatherd that I've seen before include "one looking after kids" , "Great hod (anag.)" .)

I've seen this clue in The Guardian.

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