Drink upset and spilled occasionally (6)
I believe the answer is:
tipple
'drink' is the definition.
(I know that tipple is a type of drink)
'upset and spilled occasionally' is the wordplay.
'upset' becomes 'tip' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'occasionally' means one should take alternating letters.
The alternate letters of 'spilled' are 'ple'.
'tip'+'ple'='TIPPLE'
(Other definitions for tipple that I've seen before include "Paint < pot" , "pint?" , "Habitually drink in small quantities" , "fall" , "Alcoholic liquor" .)