Just one short month in the countryside calendar (3)

I believe the answer is:

dec

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'just one short month' is the definition.
'Dec' can be an answer for 'month' (abbreviation for December). I'm not certain of the 'just one short' bit.

'in the countryside calendar' is the wordplay.
'in' indicates a hidden word.
'DEC' is hidden within 'countryside calendar'.

Can you help me to learn more?

(Other definitions for dec that I've seen before include "Ant's TV partner" , "Ant's Geordie mate on Saturday night" .)

I've seen this clue in the Evening Standard.

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