Difficulty undoing case with bolt (8)
I believe the answer is:
obstacle
'difficulty' is the definition.
(I know that obstacle is a type of balk)
'undoing case with bolt' is the wordplay.
'undoing' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'case'+'bolt'='casebolt'
'casebolt' with letters rearranged gives 'OBSTACLE'.
(Other definitions for obstacle that I've seen before include "Barrier or deterrent" , "Thing that obstructs progress" , "Progress blocker" , "Maybe let" , "bar" .)