Truck departs with fish (4)
I believe the answer is:
dray
'truck' is the definition.
(thesaurus)
'departs with fish' is the wordplay.
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'with' is a charade indicator (letters next to each other).
'fish' becomes 'ray' (ray is a kind of fish).
'd'+'ray'='DRAY'
(Other definitions for dray that I've seen before include "Brewery wagon" , "Brewer's horse-drawn cart" , "delivery vehicle" , "Low truck" , "Heavy load-carrying vehicle" .)