It's likely belligerent Olympian features in papers always (1,7)
I believe the answer is:
i daresay
'it's likely' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'belligerent olympian features in papers always' is the wordplay.
'belligerent olympian' becomes 'ares' (I've seen this in another clue).
'features in' indicates putting letters inside.
'papers' becomes 'ID' (identifying documents are one's 'papers').
'always' becomes 'ay' (archaic term for 'always').
'id'+'ay'='iday'
'ares' going within 'iday' is 'I DARESAY'.
Can you help me to learn more?
(Other definitions for i daresay that I've seen before include "Probably" , "Maybe" , "Methinks it's likely that" .)