Blood spilt ultimately in support of county (6)
I believe the answer is:
claret
'blood' is the definition.
(claret can informally mean blood)
'spilt ultimately in support of county' is the wordplay.
'ultimately' indicates one should take the final letters.
'in support of' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'county' becomes 'Clare' (county of Ireland).
The last letter of 'spilt' is 't'.
't' after 'clare' is 'CLARET'.
(Other definitions for claret that I've seen before include "Dry red wine of Bordeaux" , "Cartel for Bordeaux red wine" , "Dark purplish-red colour" , "Purplish-red - blood" , "in one's veins?" .)