Crew, ultimate of those names at sea (6)
I believe the answer is:
seamen
'crew ultimate of those names at sea' is the definition.
I can't judge whether this definition defines the answer.
'ultimate of those names at sea' is the wordplay.
'ultimate of' says to take the final letters (I've seen 'ultimate' mean this).
'at sea' indicates anagramming the letters.
The last letter of 'those' is 'e'.
'e'+'names'='enames'
'enames' anagrammed gives 'SEAMEN'.
Can you help me to learn more?
(Other definitions for seamen that I've seen before include "Sailors" , "mates, maybe" .)