Down tools when chief departs in small vehicle (5)
I believe the answer is:
trike
'small vehicle' is the definition.
(short for tricycle; 'small' indicates a short form)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for trike that I've seen before include "Tricycle (inf.)" , "Child's vehicle" , "Three-wheeled cycle" , "Three-wheeled vehicle" , "transport system" .)