Lord of most of Kent region (5)
I believe the answer is:
thane
'lord' is the definition.
(thane is a kind of lord)
'most of kent region' is the wordplay.
'most of' means to remove the last letter.
'kent region' becomes 'thanet'.
'thanet' with its last letter removed is 'THANE'.
'of' acts as a link.
(Other definitions for thane that I've seen before include "Macbeth was made -- of Cawdor" , "Anglo-Saxon noble of lower rank" , "Anglo-Saxon aristocrat - old Scottish clan chief" , "Macbeth became - of Cawdor" , "Medieval lord" .)