Avenging spirits in Greece or Ireland? Certainly! (7)
I believe the answer is:
erinyes
'avenging spirits in greece' is the definition.
'ireland? certainly' is the wordplay.
'ireland?' becomes 'erin'.
'certainly' becomes 'yes' (I've seen this before).
'erin'+'yes'='ERINYES'
'or' is the link.
(Other definitions for erinyes that I've seen before include "Monsters" , "Snake-haired creatures" , "Furies (Greek myth)" , "Snake-haired goddesses" , "Fury repeatedly" .)