High notes wobbly over beginning of duet (6)
I believe the answer is:
stoned
'high' is the definition.
(on drugs)
'notes wobbly over beginning of duet' is the wordplay.
'wobbly' indicates an anagram.
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'beginning of' suggests taking the first letters.
The initial letter of 'duet' is 'd'.
'notes' with letters rearranged gives 'stone'.
'stone'+'d'='STONED'
(Other definitions for stoned that I've seen before include "Completely under the influence" , "Are cherries so" , "Bombed" , "High on drugs or alcohol" , "Stephen thus martyred" .)