Artfully resets a mosaic tile (7)
I believe the answer is:
tessera
'mosaic tile' is the definition.
(I've seen this before)
'artfully resets a' is the wordplay.
'artfully' indicates anagramming the letters.
'resets' is an anagram of 'tesser'.
'tesser'+'a'='TESSERA'
(Other definitions for tessera that I've seen before include "small bit of artwork" , "only part of the picture" , "Reseats (anag) -- small tile used in a mosaic" , "Bit of mosaic" , "Small mosaic piece" .)