Preserve with difficulty? (6)
I believe the answer is:
pickle
This clue is a double definition.
'preserve' is the first definition.
(pickling is a kind of preserving)
'difficulty?' is the second definition.
(pickle is a kind of difficulty)
'with' is the link.
(Other definitions for pickle that I've seen before include "Preserve in liquid" , "Mischief-maker" , "Condiment - tricky situation - troublesome child" , "Chutney, relish, salsa etc" , "tricky spot" .)