Crew member: he maps it at sea (8)
I believe the answer is:
shipmate
'crew member' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'he maps it at sea' is the wordplay.
'at sea' indicates an anagram.
'he'+'maps'+'it'='hemapsit'
'hemapsit' with letters rearranged gives 'SHIPMATE'.
Can you help me to learn more?
(Other definitions for shipmate that I've seen before include "Fellow sailor" , "Fellow crew member" , "Fellow crewman" , "Colleague on board" , "Fellow seaman" .)