User of rack perhaps right to be fitted in large open-top car (8)
I believe the answer is:
torturer
'user of rack' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'right to be fitted in large open-top car' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'to be fitted in' means one lot of letters goes inside another.
'large open top car' becomes 'tourer' (I am not sure about this - if you are sure you should believe this answer much more).
'rt' placed into 'tourer' is 'TORTURER'.
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for torturer that I've seen before include "One inflicting pain" , "One deliberately causing great suffering" , "One using, eg, rack" , "One who intentionally inflicts great pain" .)