Dutch woman is Utrecht's ultimate 20th-century artist (7)
I believe the answer is:
dadaist
'20th-century artist' is the definition.
'dutch woman is utrecht's ultimate' is the wordplay.
'dutch' becomes 'd' (common abbreviation).
'woman' becomes 'ada'.
'ultimate' suggests the final letters.
The last letter of 'utrecht' is 't'.
'd'+'ada'+'is'+'t'='DADAIST'
(Other definitions for dadaist that I've seen before include "Artist favouring irreverence and incongruity" , "supporter of nihilism" , "unconventional painter" , "Member of nihilistic art movement of early 20th century" , "Absurdist artist" .)