Momentous first over replayed in Chinnappampatti primarily, after he’s introduced! (8)
I believe the answer is:
historic
'momentous' is the definition.
(I've seen this before)
'first over replayed in chinnappampatti primarily after he's introduced' is the wordplay.
'first over' becomes 'o' (hst letter of 'over').
'primarily' indicates taking the first letters.
'after' says to put letters next to each other.
'he's introduced' becomes 'hist' (I can't explain this - if you can you should believe this answer much more).
The first letters of 'replayed in chinnappampatti' is 'ric'.
'o'+'ric'='oric'
'oric' after 'hist' is 'HISTORIC'.
Can you help me to learn more?
(Other definitions for historic that I've seen before include "Of significance in the past" , "Pertaining to what is important in the past" , "Memorable" , "Famous, important" , "Significant" .)