Horse following flag of country (5)
I believe the answer is:
irish
'country' is the definition.
(Irish is an example)
'horse following flag' is the wordplay.
'horse' becomes 'h' ('H' can be a synonym of 'horse').
'following' says to put letters next to each other.
'flag' becomes 'iris' ('iris' can be a synonym of 'flag').
'h' put after 'iris' is 'IRISH'.
'of' is the link.
(Other definitions for irish that I've seen before include "of Hibernia" , "From Dublin maybe" , "Kind of whiskey" , "One setter" , "Gaelic language" .)