A whaling captain and yes - a seaman! (4)
I believe the answer is:
ahab
'a whaling captain' is the definition.
(I've seen this before)
'yes a seaman' is the wordplay.
'yes' becomes 'ah' (I can't justify this - if you can you should give a lot more credence to this answer).
'a seaman' becomes 'ab' (short for able seaman).
'ah'+'ab'='AHAB'
'and' is the link.
Can you help me to learn more?
(Other definitions for ahab that I've seen before include "Captain hunting Moby Dick" , "Name of captain seeking Moby Dick" , "Fictional whaler" , "Whaling Captain" , "Captain of the whaler Pequod" .)