Bar on a boat - the one the navigator, of course, is holding on to (6)
I believe the answer is:
tiller
'bar on a boat' is the definition.
(I've seen this in another clue)
'the one the navigator of course is holding on to' is the wordplay.
I cannot quite understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'one' could be 'er' (I've seen this in other clues) and 'er' is found within the answer.
The remaining letters 'ill' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tiller that I've seen before include "It controls rudder manually" , "Boat steering gear" , "Ploughman - helm" , "Lever for turning the rudder" , "used to steer" .)