Artist erasing one sizable figure (5)
I believe the answer is:
titan
'sizable figure' is the definition.
(type of giant god in mythology)
'artist erasing one' is the wordplay.
I cannot quite see how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is found in the answer.
The remaining letters 'tit' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for titan that I've seen before include "Old Greek god or very strong person" , "A giant; Saturn moon" , "Atlas, possibly" , "Prometheus, for instance" , "One of elder gods defeated by Zeus" .)