Ill feeling (3,5)
I believe the answer is:
bad blood
'ill feeling' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bad blood that I've seen before include "Ill feeling of tainted sanguinary sort" , "Feeling of animosity or hostility" , "Ill-feeling (between people)" , "Ill feeling, animosity of sanguinary sort" , "Hostile feeling" .)