Difficulty (7)
'difficulty' is the definition.
(trouble can mean a difficult situation)
This is the entire clue.
(Other definitions for trouble that I've seen before include "Difficulty; public disorder" , "'A... shared is a... halved'" , "Dire straits" , "Hassle" , "Disturb; unpleasantness" .)
'difficulty' is the definition.
(I know that problem is a type of difficulty)
This is all the clue.
(Other definitions for problem that I've seen before include "Matter hard to cope with" , "Difficulty to be solved" , "State of difficulty that needs to be resolved" , "Difficult matter; puzzle" , "Quandary or dilemma" .)