National flag at entrance to Holy Island (8)
I believe the answer is:
irishman
'national' is the definition.
(someone from Ireland)
'flag at entrance to holy island' is the wordplay.
'flag' becomes 'iris' (type of iris flower).
'at' is a charade indicator (letters next to each other).
'entrance to' indicates taking the first letters.
'island' becomes 'man' (the Isle of Man is an example).
The first letter of 'holy' is 'h'.
'iris'+'h'+'man'='IRISHMAN'
(Other definitions for irishman that I've seen before include "Dubliner, say" , "One from Eire" , "Eg, Dublin male" , "Dublin native" , "Paddy" .)