Brilliant Adrian wasted time (7)
I believe the answer is:
radiant
'brilliant' is the definition.
(I've seen this before)
'adrian wasted time' is the wordplay.
'wasted' indicates an anagram.
'time' becomes 't' (abbreviation).
'adrian' anagrammed gives 'radian'.
'radian'+'t'='RADIANT'
(Other definitions for radiant that I've seen before include "beaming with joy" , "Lit up" , "Very rich (7.2.2)" , "Dazzling" , "Effulgent" .)