Unruffled by prophet in conversation about space (6)
I believe the answer is:
serene
'unruffled' is the definition.
(thesaurus)
'prophet in conversation about space' is the wordplay.
'prophet' becomes 'seer' (I've seen this before).
'in conversation' shows a homophone (sound like).
'about' says the letters should be written in reverse.
'space' becomes 'en'.
'seer' sounds like 'sere'.
'en' written backwards gives 'ne'.
'sere'+'ne'='SERENE'
'by' is the link.
(Other definitions for serene that I've seen before include "Impassive" , "Peaceful and calm in manner" , "Calm and unclouded" , "Calm and unruffled, like a princely title." , "Calm, peaceful, tranquil" .)