Popular friends welcoming occasionally staid friends (9)
I believe the answer is:
intimates
'friends' is the definition.
(intimate is a kind of friend)
'popular friends welcoming occasionally staid' is the wordplay.
'popular' becomes 'in'.
'friends' becomes 'mates' (mate is a kind of friend**).
'welcoming' is an insertion indicator (in sense of 'inviting in').
'occasionally' indicates alternate letters.
The alternate letters of 'staid' are 'ti'.
'in'+'mates'='inmates'
'inmates' going around 'ti' is 'INTIMATES'.
(Another definition for intimates that I've seen is " Hints - close friends".)