Somewhat insult ancient ruler (6)
I believe the answer is:
sultan
'ruler' is the definition.
(sultan is a kind of ruler)
'somewhat insult ancient' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'SULTAN' is hidden within 'insult ancient'.
(Other definitions for sultan that I've seen before include "Turkish ruler" , "Chicken" , "Ottoman emperor" , "one ruling the roost?" , "Muslim ruler" .)