Popular type from a forecourt showing off a Citroen from lock-up (13)
I believe the answer is:
incarceration
'lock-up' is the definition.
I can't tell whether this defines the answer.
'popular type from a forecourt showing off a citroen' is the wordplay.
'popular' becomes 'in'.
'type from a forecourt showing' becomes 'car' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'off' indicates anagramming the letters.
'a'+'citroen'='acitroen'
'acitroen' anagrammed gives 'ceration'.
'in'+'car'+'ceration'='INCARCERATION'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for incarceration that I've seen before include "Imprisonment" , "Jail" , "Captivity" , "Judicial confinement" .)