Condemn Dune once shot (8)
I believe the answer is:
denounce
'condemn' is the definition.
(I've seen this before)
'dune once shot' is the wordplay.
'shot' indicates anagramming the letters.
'dune'+'once'='duneonce'
'duneonce' anagrammed gives 'DENOUNCE'.
(Other definitions for denounce that I've seen before include "Speak publicly against, censure" , "Condemn publicly" , "Accuse publicly" , "Speak publicly or give information against" , "Inform against (someone)" .)