Keys getting mounted and confined (9)

I believe the answer is:

bedridden

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'confined' is the definition.
(thesaurus)

'keys getting mounted and' is the wordplay.
'keys' becomes 'de' (I've seen this in other clues).
'getting' says to put letters next to each other.
'mounted' becomes 'bedrid' (I am not sure about this - if you are sure you should believe this answer much more).
'and' becomes 'n' (common abbreviation for 'and').
'de' put after 'bedrid' is 'bedridde'.
'bedridde'+'n'='BEDRIDDEN'

Can you help me to learn more?

(Other definitions for bedridden that I've seen before include "laid up" , "permanently retired" , "Unwell" .)

I've seen this clue in The Daily Express.

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