Man in control of sea-level, one supposes erroneously (5)
I believe the answer is:
moses
'man' is the definition.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for moses that I've seen before include "Hebrew leader and lawgiver" , "One given tablets" , "He led the Jews towards the Promised Land" , "Biblical leader across the Red Sea" , "Liberator" .)