French are getting behind petition to host one group of stars (8)
I believe the answer is:
pleiades
'group of stars' is the definition.
(I've seen this before)
'french are getting behind petition to host one' is the wordplay.
'french are' becomes 'es' ('are' in French).
'getting behind' says to put letters next to each other (some letters go behind others).
'petition' becomes 'plead' (I've seen this in another clue).
'to host' indicates putting letters inside (inserted letters are hosted or welcomed).
'one' becomes 'i' (Roman numeral).
'plead' going around 'i' is 'pleiad'.
'es' put after 'pleiad' is 'PLEIADES'.
(Other definitions for pleiades that I've seen before include "Conspicuous star cluster in Taurus" , "Group of sisters" , "Daughters of Atlas - Seven Sisters star cluster in Taurus" , "Group of stars in Taurus" , "Prominent star group" .)