Tactful Native American in western half of region (8)
I believe the answer is:
discreet
'tactful' is the definition.
(similar in meaning)
'native american in western half of region' is the wordplay.
'native american' becomes 'cree' (an indigenous people of North America).
'in' is an insertion indicator.
'western half of' means to take half the letters.
'region' becomes 'district' (district is a kind of region).
'district' halved is 'dist'.
'cree' inserted inside 'dist' is 'DISCREET'.
(Other definitions for discreet that I've seen before include "Doesn't give away secrets - can be trusted" , "Careful in keeping a secret" , "Diplomatic" , "Careful in not attracting attention" , "Showing prudence and circumspection" .)