Debussy's prelude has odd beat (4)
I believe the answer is:
drum
'beat' is the definition.
(I know that beat can be written as drum)
'debussy's prelude has odd' is the wordplay.
'prelude' suggests taking the first letters (a prelude is an introduction).
'has' says to put letters next to each other.
'odd' becomes 'rum' (rum can mean strange or dubious).
The first letter of 'debussys' is 'd'.
'd'+'rum'='DRUM'
(Other definitions for drum that I've seen before include "See 16" , "Mus. instrument; container" , "Iris rootstock (perfume)" , "house" , "Percussion instrument" .)