Strict doctor with a prisoner, a Scot (9)
I believe the answer is:
draconian
'strict' is the definition.
(thesaurus)
'doctor with a prisoner a scot' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'with' indicates putting letters inside.
'a prisoner' becomes 'con' (abbreviation for 'convict').
'scot' becomes 'ian'.
'a'+'ian'='aian'
'con' put into 'aian' is 'aconian'.
'dr'+'aconian'='DRACONIAN'
(Other definitions for draconian that I've seen before include "Excessively severe" , "Very strict" , "Cruel" , "Hard" , "Savage" .)