Criminal allied with yob in court (3,6)
I believe the answer is:
old bailey
'court' is the definition.
(famous English courthouse)
'criminal allied with yob' is the wordplay.
'criminal' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'allied' after 'yob' is 'yoballied'.
'yoballied' anagrammed gives 'OLD BAILEY'.
'in' acts as a link.
(Other definitions for old bailey that I've seen before include "Courts" , "suitable for trial in London" , "Central Criminal Court in London" , "London's Central Criminal Court" .)