Suggestion from monarch in trouble (4)
I believe the answer is:
hint
'suggestion' is the definition.
(I know that suggestion can be written as hint)
'from monarch in trouble' is the wordplay.
'from' says the answer is hidden in the clue.
'HINT' can be found hidden inside 'monarch in trouble'.
(Other definitions for hint that I've seen before include "'Slight indication, indirect suggestion (4)'" , "suspicion" , "Imply, suggest" , "CRT screen coating" , "Small trace; clue" .)