Assistant in hospital nursing a gruff invalid (9)

I believe the answer is:

suffragan

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'assistant' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see a link between them that I can't see?

'hospital nursing a gruff invalid' is the wordplay.
'hospital' becomes 'san' (I've seen this before).
'nursing' is an insertion indicator.
'invalid' indicates anagramming the letters.
'a'+'gruff'='agruff'
'agruff' is an anagram of 'uffrag'.
'san' placed around 'uffrag' is 'SUFFRAGAN'.

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.

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