County's essence given the mark of choice? (5)

I believe the answer is:

essex

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'county's' is the definition.
(English county)

'essence given the mark of choice?' is the wordplay.
'essence' becomes 'esse' (I've seen this in another clue).
'given' says to put letters next to each other.
'the mark of choice?' becomes 'x' (I am not sure about this - if you are sure you should believe this answer much more).
'esse'+'x'='ESSEX'

Can you help me to learn more?

(Other definitions for essex that I've seen before include "County cricket team" , "County near London" , "Queen's favourite" , "County, its tasteless moneyed Man" , "Ancient kingdom" .)

I've seen this clue in The Times.

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