The one left in a vessel who can set a course? (5)
I believe the answer is:
pilot
'set a course?' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'the one left in a vessel' is the wordplay.
'the one' becomes 'I' (Roman numeral).
'left' becomes 'l' (common abbreviation).
'in' means one lot of letters goes inside another.
'a vessel' becomes 'pot' (type of container).
'i'+'l'='il'
'il' inserted into 'pot' is 'PILOT'.
'who can' acts as a link.
Can you help me to learn more?
(Other definitions for pilot that I've seen before include "One who brings a vessel into port" , "He steers ship or plane" , "Plane operator" , "air traffic controller?" , "Steer, test (scheme)" .)