One in conspiracy to control the ship (5)
I believe the answer is:
pilot
'control the ship' is the definition.
'pilot' can be an answer for 'control' (piloting is a kind of controlling). I am not certain of the 'the ship' bit.
'one in conspiracy' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' indicates putting letters inside.
'conspiracy' becomes 'plot' (a conspiracy is a secret plot).
'i' inserted within 'plot' is 'PILOT'.
'to' is the link.
Can you help me to learn more?
(Other definitions for pilot that I've seen before include "Flier of aircraft" , "This person can be found in a plane or a boat" , "Name of Mr Rochester's dog" , "Lead" , "air traffic controller?" .)