Well-known ma of lawless American (6)
I believe the answer is:
famous
'well-known' is the definition.
(I've seen this before)
'ma of lawless american' is the wordplay.
'lawless' indicates an anagram.
'american' becomes 'us' (abbreviation for United States).
'ma'+'of'='maof'
'maof' anagrammed gives 'famo'.
'famo'+'us'='FAMOUS'
(Other definitions for famous that I've seen before include "Known and esteemed" , "Renowned, celebrated" , "Widely known and notable" , "Acclaimed" , "Known to very many people" .)