Starts to justify expense equipping public service vehicles (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
jeeps
'vehicles' is the definition.
(jeep is a kind of vehicle)
'starts to justify expense equipping public service' is the wordplay.
'starts to' says to take the initial letters.
The initial letters of 'justify expense equipping public service' is 'JEEPS'.
(Other definitions for jeeps that I've seen before include "Military vehicles" , "Military trucks" .)