Model Sierra, almost market leader in UK soon? (4,7)

I believe the answer is:

keir starmer

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'leader in uk soon?' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'model sierra almost market' is the wordplay.
'model' is an anagram indicator (the solver must model the letters into a new form).
'almost' means to remove the last letter (most of the word but not all of it).
'sierra' with its final letter taken away is 'sierr'.
'sierr'+'market'='sierrmarket'
'sierrmarket' anagrammed gives 'KEIR STARMER'.

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I've seen this clue in The Independent.

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