Letter from Rochdale physician (5)

I believe the answer is:

aleph

'letter' is the definition.
(aleph is a kind of letter)

'from rochdale physician' is the wordplay.
'from' says the answer is hidden in the clue.
'ALEPH' is hidden within 'rochdale physician'.

(Other definitions for aleph that I've seen before include "letter in Middle East" , "Abroad, a" , "First character" , "First letter of the Hebrew alphabet" , "Sign of a beast? A Phoenician" .)

I've seen this clue in The Telegraph.

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