Adolf could have been lither! (6)
I believe the answer is:
hitler
'adolf' is the definition.
(I've seen this in another clue)
'have been lither' is the wordplay.
'lither' can be anagrammed to 'HITLER'.
Though, I am unsure how this is indicated.
'could' is the link.
Can you help me to learn more?
(Other definitions for hitler that I've seen before include "German dictator" , "Der Fuhrer" , "German F?hrer" , "See 20" , "Nazi dictator" .)