Singular character departs on a trip (6)
I believe the answer is:
stoned
'on a trip' is the definition.
(I've seen this before)
'singular character departs' is the wordplay.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'character' becomes 'tone' (tone can mean a character or mood).
'departs' becomes 'd' (abbreviation used in transport schedules).
's'+'tone'+'d'='STONED'
(Other definitions for stoned that I've seen before include "Slangily drunk in Ostend" , "High; intoxicated" , "Are cherries so" , "Under the influence of drugs (colloq.)" , "attacked with missiles" .)