Crossword Genius

Cosmetic: not the best for much longer? (9,5)

Ross

I believe the answer is:

vanishing cream

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

'not the best for much longer?' is the wordplay.
I cannot really understand how this works, but
'best' could be 'cream' (as in 'the cream of the crop') and 'cream' is found within the answer.
The remaining letters 'vanishing' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

(Other definitions for vanishing cream that I've seen before include "foundation?" , "Brain Drain" , "Cosmetic" .)

I've seen this clue in The Times.
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