Some heathen celebrated from this time (5)
I believe the answer is:
hence
'from this time' is the definition.
(I've seen this before)
'some heathen celebrated' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'HENCE' can be found hidden inside 'heathen celebrated'.
(Other definitions for hence that I've seen before include "It follows from that fact" , "From this place or time" , "For this reason; in the future" , "From this time, or for this reason" , "Thus" .)