Nerd wasted a krona (6)
I believe the answer is:
anorak
'nerd' is the definition.
'wasted a krona' is the wordplay.
'wasted' indicates anagramming the letters.
'a'+'krona'='akrona'
'akrona' anagrammed gives 'ANORAK'.
(Other definitions for anorak that I've seen before include "Garment (worn by boring obsessive?)" , "trainspotter" , "European currency" , "Coat - trivia expert?" , "Dull person" .)