Cool and calm, the pig wallowing (10)
I believe the answer is:
phlegmatic
'cool' is the definition.
(I've seen this before)
'calm the pig wallowing' is the wordplay.
'wallowing' is an anagram indicator (I've seen 'wallow' mean this).
'calm'+'the'+'pig'='calmthepig'
'calmthepig' is an anagram of 'PHLEGMATIC'.
'and' acts as a link.
(Other definitions for phlegmatic that I've seen before include "Unemotional" , "Unexcitable" , "cool" , "dull and lifeless" , "Calm; philosophical" .)