Old man eating chicken -- sign that could portend prodigious events (9)
I believe the answer is:
phenomena
'events' is the definition.
(phenomenon is a kind of event)
'old man eating chicken sign' is the wordplay.
'old man' becomes 'pa' (both can mean father).
'eating' is an insertion indicator.
'chicken' becomes 'hen' (hen is a kind of chicken).
'sign' becomes 'omen' (omen is a kind of sign).
'hen'+'omen'='henomen'
'pa' placed around 'henomen' is 'PHENOMENA'.
'that could portend prodigious' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for phenomena that I've seen before include "strange doings!" , "facts" , "Things sensed" , "Remarkable events or things, wonders (9)" , "He-man open to remarkable things or wonders" .)