Photograph yuletide saint and queen outside diner (9)

I believe the answer is:

picnicker

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'outside diner' is the definition.
(someone dining outside)

'photograph yuletide saint and queen' is the wordplay.
'photograph' becomes 'pic' (short for picture).
'yuletide saint' becomes 'nick' (I can't justify this - if you can you should believe this answer much more).
'and' says to put letters next to each other.
'queen' becomes 'ER' (short for Elizabeth Regina ie Queen Elizabeth).
'pic'+'nick'+'er'='PICNICKER'

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I've seen this clue in The Times.

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