Disaffect with a crooked line on a half term (8)
I believe the answer is:
alienate
'disaffect' is the definition.
(synonyms)
'a crooked line on a half term' is the wordplay.
'crooked' indicates an anagram.
'on' is an insertion indicator (as in clothing 'on' a person).
'half' means to take half the letters.
'line' is an anagram of 'lien'.
'a' placed into 'lien' is 'alien'.
'term' cut in half is 'te'.
'alien'+'a'+'te'='ALIENATE'
'with' is the link.
(Other definitions for alienate that I've seen before include "Estrange, disaffect" , "transfer" , "Lose support of" , "Turn away from" , "Cause a friend to become hostile" .)