Vehicle with a screw loose on purpose (10)
I believe the answer is:
locomotive
'vehicle' is the definition.
(I know that locomotive is a type of self-propelled vehicle)
'a screw loose on purpose' is the wordplay.
'a screw loose' becomes 'loco' (I can't justify this - if you can you should believe this answer much more).
'on' says to put letters next to each other.
'purpose' becomes 'motive' (I've seen this before).
'loco'+'motive'='LOCOMOTIVE'
'with' is the link.
Can you help me to learn more?
(Other definitions for locomotive that I've seen before include "for moving from place to place" , "Able to move by oneself" , "Rocket, perhaps" , "one's attached to the train" , "Railway engine" .)