£50 in bank that navigator gets hold of (6)
I believe the answer is:
tiller
'that navigator gets hold of' is the definition.
(a ship's navigator uses a tiller)
'ps50 in bank' is the wordplay.
'ps50' becomes 'll' (I am not sure about this - if you are sure you should believe this answer much more).
'in' is an insertion indicator.
'bank' becomes 'tier' (I've seen this before).
'll' inserted within 'tier' is 'TILLER'.
(Other definitions for tiller that I've seen before include "Steering device -- ploughman" , "It moves a rudder" , "Rudder's steering handle" , "Lever to move a boat's rudder" , "Boat's steering mechanism" .)