A land governed by the same chief (6)
I believe the answer is:
domain
'a land' is the definition.
(I know that land can be written as domain)
'by the same chief' is the wordplay.
'by' means one lot of letters go next to another.
'the same' becomes 'do' (abbreviation for ditto).
'chief' becomes 'main' (synonyms).
'do' next to 'main' is 'DOMAIN'.
'governed' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for domain that I've seen before include "A district sphere of influence" , "Sphere of activity" , "Scope of knowledge - owned land" , "Range of influence or field of activity" , "Range of influence or field of thought" .)