Location of the difficulty? (3)
I believe the answer is:
fix
I believe this clue is a double definition.
'location' is the first definition.
('fix' can be a synonym of 'location')
'the difficulty?' is the second definition.
(fix is a kind of difficulty)
'of' is the link.
(Other definitions for fix that I've seen before include "Mend" , "Arrange" , "mess" , "Fasten" , "Predicament" .)