Northern stars returning for festival (4)
I believe the answer is:
noel
'festival' is the definition.
(I have seen 'Religious festival' mean 'noel' so perhaps 'festival' could also mean 'noel')
'northern stars returning' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'stars' becomes 'leo' (I've seen this before).
'returning' is a reversal indicator.
'leo' backwards is 'oel'.
'n'+'oel'='NOEL'
'for' acts as a link.
(Other definitions for noel that I've seen before include "Coward who wrote and acted, d. 1973" , "Fellow" , "Christmas, esp. in carols; boy's name" , "Girl - boy - Christmas" , "See 7 Across" .)