Royal heir and wife unwell one morning (7)

I believe the answer is:

william

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'royal heir' is the definition.
The definition suggests a singular noun which matches the answer.

'wife unwell one morning' is the wordplay.
'wife' becomes 'w' (abbreviation).
'unwell' becomes 'i'll' (similar in meaning).
'one' becomes 'i' (Roman numeral).
'morning' becomes 'am' (as in 12:00 AM).
'w'+'ill'+'i'+'am'='WILLIAM'

'and' acts as a link.

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(Other definitions for william that I've seen before include "Boy's name" , "Norman conqueror" , "See 20" , "Bill" , "I am a weakish speller (anag) -- author" .)

I've seen this clue in The Telegraph.

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