Odd drink sent back causes uproar (6)
I believe the answer is:
rumpus
'uproar' is the definition.
(thesaurus)
'odd drink sent back' is the wordplay.
'odd' becomes 'rum' (I've seen this before).
'drink' becomes 'sup' (I've seen this before).
'sent back' says the letters should be written backwards.
'sup' written backwards gives 'pus'.
'rum'+'pus'='RUMPUS'
'causes' acts as a link.
(Other definitions for rumpus that I've seen before include "Harsh rough nature" , "Noisy, disruptive commotion" , "Uproar or angry dispute" , "To-do" , "5a [BALLYHOO] involving noise" .)