Timid wren flying when it's really cold (9)

I believe the answer is:

midwinter

'when it's really cold' is the definition.

'timid wren flying' is the wordplay.
'flying' indicates an anagram.
'timid'+'wren'='timidwren'
'timidwren' anagrammed gives 'MIDWINTER'.

(Other definitions for midwinter that I've seen before include "Bleakest time of year?" , "height of season?" , "Date of holy birth" .)

I've seen this clue in The Independent.

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