Strain first Italian vehicle (4)
I believe the answer is:
taxi
'vehicle' is the definition.
(taxi is a kind of vehicle)
'strain first italian' is the wordplay.
'strain' becomes 'tax' (taxing is a kind of straining).
'first' says to take the initial letters.
The initial letter of 'italian' is 'i'.
'tax'+'i'='TAXI'
(Other definitions for taxi that I've seen before include "Rank occupant" , "Motor vehicle by rank?" , "Minicab" , "Danny DeVito sitcom" , "people carrier?" .)