Bad language of British legislating to be reviewed (12)
I believe the answer is:
billingsgate
'bad language' is the definition.
(thesaurus)
'british legislating to be reviewed' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'to be reviewed' indicates an anagram (To look at again and re view).
'legislating' with letters rearranged gives 'illingsgate'.
'b'+'illingsgate'='BILLINGSGATE'
'of' is the link.
(Other definitions for billingsgate that I've seen before include "Swearing" , "London fish market" .)