Ill-feeling as a friend buttons lip (8)
I believe the answer is:
acrimony
'ill-feeling' is the definition.
(I've seen this before)
'a friend buttons lip' is the wordplay.
'friend' becomes 'cony' (cony can be a term of endearment).
'buttons' means one lot of letters goes inside another (button can mean to fasten or contain using buttons).
'lip' becomes 'rim' (synonyms).
'cony' placed around 'rim' is 'crimony'.
'a'+'crimony'='ACRIMONY'
'as' is the link.
(Other definitions for acrimony that I've seen before include "Bitterness or ill-feeling" , "poison" , "Bitterness of manner or words" , "'Bitterness, acerbity (8)'" , "I cry, moan (anag)" .)