Nationality of flag on top of hotel (5)
I believe the answer is:
irish
'nationality' is the definition.
(Irish is an example)
'flag on top of hotel' is the wordplay.
'flag' becomes 'iris' (type of iris flower).
'on top of' suggests taking the first letters.
The initial letter of 'hotel' is 'h'.
'iris'+'h'='IRISH'
'of' acts as a link.
(Other definitions for irish that I've seen before include "Native to Erin" , "Relating to Ireland" , "Native to the Emerald Isle" , "From Cork, for instance" , "Hi, Sir, ar you a Celt?" .)