VAT, perhaps, with one hire car (4)
I believe the answer is:
taxi
'hire car' is the definition.
(I've seen this before)
'vat perhaps with one' is the wordplay.
'vat perhaps' becomes 'tax' (vat is a kind of tax).
'with' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral**).
'tax'+'i'='TAXI'
(Other definitions for taxi that I've seen before include "people carrier?" , "Danny DeVito sitcom" , "Motor-cab" , "At airport, guide" , "US currency" .)