Possibly see about a relaxation (4)
I believe the answer is:
ease
'relaxation' is the definition.
('ease' can be a synonym of 'relaxation')
'possibly see about a' is the wordplay.
'possibly' indicates an anagram.
'about' indicates putting letters inside.
'see' is an anagram of 'ese'.
'ese' going around 'a' is 'EASE'.
(Other definitions for ease that I've seen before include "Move gently or carefully" , "nonchalance!" , "Relief" , "Allay" , "Lack of difficulty" .)