Nile queen, informally (4)
I believe the answer is:
cleo
'nile queen informally' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cleo that I've seen before include "She ruled" , "Dame Laine" , "Carry on -- (1964 film)" , "Woman" , "Jazz singer, ___ Laine" .)