Duke with odd instrument (4)
I believe the answer is:
drum
'instrument' is the definition.
(I know that drum is a drum)
'duke with odd' is the wordplay.
'duke' becomes 'd' (abbreviation).
'with' is a charade indicator (letters next to each other).
'odd' becomes 'rum' (rum can mean strange or dubious).
'd'+'rum'='DRUM'
(Other definitions for drum that I've seen before include "nightclub" , "beat" , "(Revolving) cylinder" , "Percussion instrument" , "Introductory beats" .)