Uncompromising princess leaves the region (6)
I believe the answer is:
strict
'uncompromising' is the definition.
(I've seen this in another clue)
'princess leaves the region' is the wordplay.
'princess' becomes 'di' (Princess Diana).
'leaves' suggests deleting specific letters.
'the region' becomes 'district' (district is a kind of region).
'district' with 'di' taken out is 'STRICT'.
(Other definitions for strict that I've seen before include "Austere - rigid" , "Excessive pride" , "Demanding that rules are observed" , "Exacting, unsparing" , "Rigidly accurate" .)