The animal upset the beer, all right (6)
I believe the answer is:
reebok
'the animal' is the definition.
(I've seen this before)
'upset the beer all right' is the wordplay.
'upset' is a reversal indicator.
'all right' becomes 'ok' ('ok' can be a synonym of 'all right').
'beer' written backwards gives 'reeb'.
'reeb'+'ok'='REEBOK'
(Other definitions for reebok that I've seen before include "African runner" , "Antelope of southern Africa" , "South African antelope (E, not H)" , "South African animal" .)