Tot before start of amusing play (5)
I believe the answer is:
drama
'play' is the definition.
(I know that play can be written as drama)
'tot before start of amusing' is the wordplay.
'tot' becomes 'dram' (both can mean an alcoholic drink).
'before' means one lot of letters go next to another.
'start of' says to take the initial letters.
The first letter of 'amusing' is 'a'.
'dram'+'a'='DRAMA'
(Other definitions for drama that I've seen before include "Turbulent emotional episode" , "Theatre or radio play" , "Theatrical work" , "Emotional situation" , "Hamlet, say" .)