Fix where water leaves back of instrument, did you say? (6)
I believe the answer is:
pickle
'fix' is the definition.
(both can mean a difficult situation)
I don't understand how the rest of the clue works.
(Other definitions for pickle that I've seen before include "Veg or fruit relish" , "Relish; preserve" , "A preserved vegetable or a fine mess" , "Preserve; mess" , "Preserve in liquid" .)