Some in triumph arise excitedly for old sectarian (8)
I believe the answer is:
pharisee
'old sectarian' is the definition.
(the Pharisees were an ancient sect)
'some in triumph arise excitedly' is the wordplay.
'some in' indicates a hidden word.
'PHARISEE' is hidden within 'triumph arise excitedly'.
'for' is the link.
(Other definitions for pharisee that I've seen before include "Member of ancient Jewish sect; Heap, sire (anag.)" , "Strict observer" , "A Biblical hypocrite" , "Hare pies for the Biblical pedant" , "Biblical follower of rules" .)