It's obvious the French are in the vehicle (5)
I believe the answer is:
clear
'it's obvious' is the definition.
(similar in meaning)
'the french are in the vehicle' is the wordplay.
'the french' becomes 'le' ('the' in French).
'are in the' indicates putting letters inside.
'vehicle' becomes 'car' (car is a kind of vehicle).
'le' going inside 'car' is 'CLEAR'.
(Other definitions for clear that I've seen before include "Lucid; to empty" , "Pellucid" , "Transparent or cloudless" , "Comprehensible" , "Obvious; remove obstructions from" .)