Radical university student revolutionised painting? (5)
I believe the answer is:
ultra
'radical' is the definition.
(synonyms)
'university student revolutionised painting?' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'student' becomes 'l' (as in L-plates for learner drivers).
'revolutionised' is a reversal indicator.
'painting?' becomes 'art' (painting is a kind of art).
'art' reversed gives 'tra'.
'u'+'l'+'tra'='ULTRA'
(Other definitions for ultra that I've seen before include "Over the top" , "Immoderate" , "Extreme (eg in fashion or politics)" , "(One who is) extreme (in eg political opinion)" , "Extreme - extremist" .)