It’s a new way to relax (3)
I believe the answer is:
'relax' is the definition.
(sitting is a type of relaxing)
'it's a new way' is the wordplay.
'a new way' indicates an anagram.
'its' is an anagram of 'SIT'.
'to' acts as a link.
(Other definitions for sit that I've seen before include "Pose (for artist)" , "(Of bird) stay on nest" , "I sell badly the cotton yarn" , "Take weight off feet" , "Serve (on jury)" .)