Malay chief somewhat open about ... (4)
I believe the answer is:
raja
'malay chief' is the definition.
(I've seen this in another clue)
'somewhat open about' is the wordplay.
'somewhat open' becomes 'ajar' (I've seen this in another clue).
'about' is a reversal indicator.
'ajar' backwards is 'RAJA'.
(Other definitions for raja that I've seen before include "Indian ruler" , "sovereign" , "Asian prince or king" , "High Indian position" , "Eastern leader" .)