Does it indicate ill humour? (6,5)

I believe the answer is:

sickly smile

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'does it indicate' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'ill humour?' is the wordplay.
'ill' becomes 'sickly' (similar in meaning).
'humour?' becomes 'smile' (I am not sure about this - if you are sure you should believe this answer much more).
'sickly'+'smile'='SICKLY SMILE'

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I've seen this clue in the Evening Standard.

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