Irish article headed by "Priest Eats Fish" (8)
I believe the answer is:
piranhas
'fish' is the definition.
(I have seen 'Ferocious fish ' mean 'piranhas' so perhaps 'fish' could also mean 'piranhas')
'irish article headed by priest eats' is the wordplay.
'irish' becomes 'IR' (abbreviation).
'article' becomes 'an' (English indefinite article).
'headed by' says to put letters next to each other.
'priest' becomes 'p' (ecclesiastical abbreviation).
'eats' becomes 'has' (I've seen this before).
'ir'+'an'='iran'
'iran' after 'p' is 'piran'.
'piran'+'has'='PIRANHAS'
(Other definitions for piranhas that I've seen before include "Carnivorous freshwater fishes" , "Ferocious fish" , "Fierce sharp-teethed fish found in the Amazon, lots of them" .)