Cause to feel isolated (8)
I believe the answer is:
alienate
'cause to feel isolated' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for alienate that I've seen before include "Cause a friend to become hostile" , "Make hostile, cause to become unfriendly" , "Estrange, disaffect" , "Lose support of" , "Distance" .)