Sick bard shows animosity (3,4)
I believe the answer is:
ill will
'animosity' is the definition.
(I've seen this before)
'sick bard' is the wordplay.
'sick' becomes 'ill' (synonyms).
'bard' becomes 'will' (William Shakespeare).
'ill'+'will'='ILL-WILL'
'shows' acts as a link.
(Other definitions for ill will that I've seen before include "causing resentment" , "Disposition of enemy" , "Hostile, unfriendly feeling" , "Animosity, hostile feeling" , "Bad feeling towards, hostility" .)