Watered-down abuse? Duel it! (6)
I believe the answer is:
dilute
'watered-down' is the definition.
(thesaurus)
'abuse? duel it' is the wordplay.
'abuse?' indicates anagramming the letters (I've seen 'abuse' mean this).
'duel'+'it'='duelit'
'duelit' is an anagram of 'DILUTE'.
(Other definitions for dilute that I've seen before include "having less concentration" , "Reduce concentration of a liquid" , "not neat" , "Tone down" , "Add water to another liquid" .)