Yellow roses are not (9)

I believe the answer is:

spineless

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

'roses are not' is the wordplay.
'roses are' becomes 'spine' (I am not sure about this - if you are sure you should believe this answer much more).
'not' becomes 'less' (I've seen this in other clues).
'spine'+'less'='SPINELESS'

Can you help me to learn more?

(Other definitions for spineless that I've seen before include "Cowardly, lacking backbone" , "Not like Mrs Tiggy-Winkle" , "Yellow" , "Weak; invertebrate" , "Craven, lacking vertebrae" .)

I've seen this clue in the Evening Standard.

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