Queen entering for an investiture (4)
I believe the answer is:
rani
'queen' is the definition.
(historical term for a Hindu queen)
'entering for an investiture' is the wordplay.
'entering' says the answer is hidden in the clue.
'RANI' is hidden within 'for an investiture'.
(Other definitions for rani that I've seen before include "Rajah's wife from Iran" , "Royal Indian female" , "Raja's queen" , "Raja's wife" , "Indian queen" .)