Imprisoned in vehicle long time, unruly adolescent catches cold (12)
I believe the answer is:
incarcerated
'imprisoned' is the definition.
('incarcerate' can be a synonym of 'imprison')
'in vehicle long time unruly adolescent catches cold' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'long time' becomes 'era' (I've seen this before).
'unruly adolescent' becomes 'ted' (reference to Teddy Boy subculture).
'catches' indicates putting letters inside.
'cold' becomes 'c' (eg on taps).
'car'+'era'+'ted'='carerated'
'carerated' enclosing 'c' is 'carcerated'.
'in'+'carcerated'='INCARCERATED'
(Other definitions for incarcerated that I've seen before include "Banged up" , "Locked up" , "Imprisoned" .)