Session: pain hosting it (7)
I believe the answer is:
sitting
'session' is the definition.
(I know that session can be written as sitting)
'pain hosting it' is the wordplay.
'pain' becomes 'sting' (sting is a kind of pain).
'hosting' means one lot of letters goes inside another (inserted letters are welcomed in or hosted).
'sting' going around 'it' is 'SITTING'.
(Other definitions for sitting that I've seen before include "Being portrayed" , "Well placed" , "On a seat" , "Session of spiritualists or court" , "such an easy target" .)