Group is backing places (5)
I believe the answer is:
sites
'places' is the definition.
(a site is a place or location)
'group is backing' is the wordplay.
'group' becomes 'set' (both can mean a collection).
'backing' says the letters should be written backwards.
'set'+'is'='setis'
'setis' written backwards gives 'SITES'.
(Other definitions for sites that I've seen before include "Locates" , "Locations or positions, as for building" , "Is set (anag)" , "places" , "internet locations" .)