Old Nixon's a criminal -- at least Blair and Clinton are these (8)
I believe the answer is:
oxonians
'least blair and clinton are these' is the definition.
The definition suggests an adverb but the answer is not.
'old nixon's a criminal' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'criminal' indicates anagramming the letters.
'nixons'+'a'='nixonsa'
'nixonsa' is an anagram of 'xonians'.
'o'+'xonians'='OXONIANS'
'at' is the link.
Can you help me to learn more?
(Other definitions for oxonians that I've seen before include "Members of Oxford University" , "college types?" .)