Britain to oversee East Indian country (6)
I believe the answer is:
brunei
'country' is the definition.
(I've seen this before)
'britain to oversee east indian' is the wordplay.
I cannot quite see how this works, but
'britain' could be 'br' (abbreviation) and 'br' is present in the answer.
'east' could be 'e' ('E' can be a synonym of 'east') and 'e' is found within the answer.
The remaining letters 'uni' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for brunei that I've seen before include "Eastern land" , "Ill" , "Southeast Asian sultanate" , "Rue bin in the sultanate" , "State on Borneo" .)