Eastern leader open to the West (4)
I believe the answer is:
raja
'eastern leader' is the definition.
(I've seen this before)
'open to the west' is the wordplay.
'open' becomes 'ajar' (similar in meaning).
'to the west' says the letters should be written backwards (letters written right to left or \'east to west\').
'ajar' in reverse letter order is 'RAJA'.
(Other definitions for raja that I've seen before include "Indian ruler" , "Indian prince or king" , "Prominent Indian" , "High Indian position" , "Asian prince or king" .)