Party member behind bill upstanding (4)
I believe the answer is:
camp
'party' is the definition.
(both can mean a group of people)
'member behind bill upstanding' is the wordplay.
'member' becomes 'mp'.
'behind' says to put letters next to each other.
'bill' becomes 'ac' (**).
'upstanding' says the letters should be written backwards.
'ac' reversed gives 'ca'.
'mp' put after 'ca' is 'CAMP'.
(Other definitions for camp that I've seen before include "Hill fort; extravagantly theatrical" , "Where erections are temporary" , "Coterie" , "Tented or other military area" , "holiday location" .)