Fantastic mosaic - but very small (9)

I believe the answer is:

subatomic

'very small' is the definition.

'fantastic mosaic but' is the wordplay.
'fantastic' indicates anagramming the letters.
'mosaic'+'but'='mosaicbut'
'mosaicbut' anagrammed gives 'SUBATOMIC'.

(Other definitions for subatomic that I've seen before include "Of smaller than elementary particles" , "Like 9 across" , "Smaller than a basic particle of matter" .)

I've seen this clue in The Independent.

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