Possible German king, say, from a vast empire (7)
I believe the answer is:
ottoman
'a vast empire' is the definition.
'ottoman' can be an answer for 'empire' (I've seen this before). I'm not sure about the 'a vast' bit.
'possible german king say' is the wordplay.
'possible german' becomes 'Otto' (Otto is a common German name).
'king say' becomes 'man' (king is a kind of man).
'otto'+'man'='OTTOMAN'
'from' is the link.
Can you help me to learn more?
(Other definitions for ottoman that I've seen before include "Am not to (anag)" , "Backless seat" , "lacking arms and backing" , "Turkish empire of over 600 years" , "Turkish empire or ling cushioned seat" .)