Eritrea’s onslaught providing cover for rebellion (7)
I believe the answer is:
treason
'rebellion' is the definition.
(I've seen this before)
'eritrea's onslaught providing cover' is the wordplay.
'cover' says the answer is hidden in the clue (I've seen 'covered' mean this (the answer is covered up by the clue)).
'TREASON' is hidden in the letters of 'eritreas onslaught providing'.
'for' acts as a link.
(Other definitions for treason that I've seen before include "attempting to overthrow the king" , "Criminal attempt to overthrow a government" , "Betraying one's country" , "Crime of national betrayal" , "One rats (anag)" .)