Ill feeling on May 1st, I suspect (9)
I believe the answer is:
animosity
'ill feeling' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
(Other definitions for animosity that I've seen before include "Feeling of ill will and hostility" , "Hostility concealed by sanity - moi?" , "Maoist yin generates spirit of hostility" , "Ill-will" , "Hatred" .)