"Moby-Dick” captain (4)
I believe the answer is:
'moby-dick 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 "Captain hunting the whale Moby-Dick" , "Israelite king" , "Husband of Jezebel" , "Name of captain seeking Moby Dick" , "Melville's whale chaser" .)