Large committee admitted to small reception (7)
I believe the answer is:
welcome
'reception' is the definition.
(thesaurus)
'large committee admitted to small' is the wordplay.
'large' becomes 'l'.
'committee' becomes 'com' (abbreviation for committee).
'admitted to' means one lot of letters goes inside another.
'small' becomes 'wee' ('wee' can be similar in meaning to 'small').
'l'+'com'='lcom'
'lcom' put into 'wee' is 'WELCOME'.
(Other definitions for welcome that I've seen before include "Greet upon arrival" , "Agreeable; greeting" , "Greet; gladly received" , "Greet warmly" , "Friendly greeting" .)