Ishmael's captain (4)
I believe the answer is:
ahab
'ishmael's captain' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ahab that I've seen before include "Jezebel's husband or captain in 'Moby Dick'" , "Spring bulbs" , "Jezebel was wife of this King of Israel" , "Jezebel's husband - Moby Dick's hunter" , "Captain of the whaler Pequod" .)