Friend working on ship (4)
I believe the answer is:
mate
'friend' is the definition.
(mate is a kind of friend)
'working on ship' is the wordplay.
I cannot quite see how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is found within the answer.
The remaining letters 'me' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mate that I've seen before include "Friend; ship's officer" , "Friend; chess ending" , "Comrade - spouse - marry" , "Team up with partner" , "Spouse on team" .)