Festival always having a Stone appearing in it (6)
I believe the answer is:
'festival' is the definition.
'always having a stone appearing in it' is the wordplay.
'always' becomes 'eer' (poetic way of saying ever).
'having' is an insertion indicator.
'a stone' becomes 'st' (abbreviation).
'appearing' becomes 'a' (this might be a standard abbreviation of which I'm unaware).
'in it' is an insertion indicator.
'eer' enclosing 'st' is 'ester'.
'ester' enclosing 'a' is 'EASTER'.
Can you help me to learn more?
(Other definitions for easter that I've seen before include "See art at this time of year" , "Festival after Lent" , "Time to parade" , "Monday of 1916 Rising" , "A terse sort of Spring festival?" .)