Navigator and policeman toil away (7)
I believe the answer is:
copilot
'navigator' is the definition.
(I know that copilot is a type of maritime pilot)
'policeman toil away' is the wordplay.
'policeman' becomes 'cop' (slang term).
'away' indicates an anagram (letters move away from their original places).
'toil' with letters rearranged gives 'ilot'.
'cop'+'ilot'='COPILOT'
'and' acts as a link.
(Other definitions for copilot that I've seen before include "Second-in-command of aeroplane" , "Airliner crew member" .)