Father, for example, welcomes post being returned to the house (10)
I believe the answer is:
parliament
'the house' is the definition.
(thesaurus)
'father for example welcomes post being returned' is the wordplay.
'father for example' becomes 'parent' (father is a kind of parent**).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'post' becomes 'mail' ('mail' can be a synonym of 'post').
'being returned' says the letters should be written in reverse.
'mail' in reverse letter order is 'liam'.
'parent' going around 'liam' is 'PARLIAMENT'.
'to' is the link.
(Other definitions for parliament that I've seen before include "Legislative body" , "Diet" , "Houses" , "UK legislature" , "Legislative assembly" .)