March marchers (5)
I believe the answer is:
irish
'march marchers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for irish that I've seen before include "Hi, Sir, become a national" , "Hi, Sir, ar you a Celt?" , "Nationality" , "From Eire" , "Native to Erin" .)