It's possibly seen round about looking calm (6)
I believe the answer is:
serene
'looking calm' is the definition.
'serene' can be an answer for 'calm' (I've seen this before). I'm unsure of the 'looking' bit.
'it's possibly seen round about' is the wordplay.
'it's possibly' indicates anagramming the letters.
'round' is an insertion indicator.
'about' becomes 're' ('re' means regarding or about).
'seen' anagrammed gives 'sene'.
'sene' enclosing 're' is 'SERENE'.
Can you help me to learn more?
(Other definitions for serene that I've seen before include "Tranquil, unruffled" , "Not agitated" , "Peaceful and contented" , "Calm and unruffled, like a princely title." , "Calm and composed" .)