Henry's wife certainly upset when beheaded, love (7)

I believe the answer is:

seymour

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'henry's wife' is the definition.
(Jane Seymour wife of Henry VIII)

'certainly upset when beheaded love' is the wordplay.
'certainly upset' becomes 'sey' (I can't explain this - if you can you should give a lot more credence to this answer).
'when beheaded' means to remove the first letter.
'love' becomes 'amour' (I've seen this before).
'amour' with its initial letter taken away is 'mour'.
'sey'+'mour'='SEYMOUR'

Can you help me to learn more?

(Other definitions for seymour that I've seen before include "See 15" , "Henry VIII's wife Jane" , "Royally, Jane" , "Jane --, queen" , "Jane -, mother of Edward VI" .)

I've seen this clue in The Everyman puzzle in The Observer.

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