Sponge falls over (5)
I believe the answer is:
dipso
'sponge' is the definition.
(both are words for alcoholics)
'falls over' is the wordplay.
'falls' becomes 'dips'.
'over' becomes 'o' (cricket abbreviation).
'dips'+'o'='DIPSO'
(Other definitions for dipso that I've seen before include "(An) alcoholic (colloq.)" , "Soak" , "A habitual 18" , "drunk" , "lush" .)