Calm in fluster? That's not right (7)
I believe the answer is:
restful
'calm' is the definition.
(restful means calm or quiet)
'fluster? that's not right' is the wordplay.
'that's not right' is an anagram indicator.
'fluster' anagrammed gives 'RESTFUL'.
'in' is the link.
(Other definitions for restful that I've seen before include "Relaxing" , "Calm" , "Soothing is required" , "Tranquil - fluster (anag)" , "Quiet, soothing" .)