Group of eight getting film after a month (5)
I believe the answer is:
octet
'group of eight' is the definition.
(I've seen this in another clue)
'film after a month' is the wordplay.
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'after' says to put letters next to each other.
'a month' becomes 'Oct' (abbreviation for October).
'et' put after 'oct' is 'OCTET'.
'getting' is the link.
(Other definitions for octet that I've seen before include "A number of musicians" , "Set of eight" , "Eightsome" , "A group of eight instruments or voices" , "Played" .)