Peaceful, undisturbed (4)
I believe the answer is:
calm
This clue is a double definition.
'peaceful' is the first definition.
(similar in meaning)
'undisturbed' is the second definition.
(thesaurus)
(Other definitions for calm that I've seen before include "Composed and collected" , "Composure or serenity" , "Placid and unruffled" , "Serene" , "Cool, not excited" .)