Conservative not happy (4)

I believe the answer is:

blue

I believe this clue is a double definition.

'conservative' is the first definition.
(I've seen this before)

'not happy' is the second definition.
(I know this)

(Other definitions for blue that I've seen before include "Colour of depression" , "Red-headed Australian" , "Sad - shade" , "Varsity sportsman" , "Sad, squander" .)

I've seen this clue in The Times.

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