Organ stop in list (8)

I believe the answer is:

This clue is a double definition.

'organ stop' is the first definition.
(thesaurus)

'list' is the second definition.
(thesaurus)

'in' is the link.

(Other definitions for register that I've seen before include "Show" , "Enrol, to vote perhaps" , "Read" , "Official record of names etc." , "(Put one's name down on) list" .)

I've seen this clue in The Telegraph and The Times.

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