Group has a place to sit (4)
I believe the answer is:
seat
'place to sit' is the definition.
(I've seen this before)
'group has a' is the wordplay.
'group' becomes 'set' (both can mean a collection).
'has' is an insertion indicator.
'set' going around 'a' is 'SEAT'.
(Other definitions for seat that I've seen before include "Somewhere to sit" , "Position (in parliament)" , "MP's place in parliament" , "Eg, chair, stool" , "Horizontal part of a chair" .)