Mixing online less creates isolation (10)
I believe the answer is:
loneliness
'isolation' is the definition.
(loneliness is a kind of isolation)
'mixing online less' is the wordplay.
'mixing' indicates an anagram.
'online'+'less'='onlineless'
'onlineless' with letters rearranged gives 'LONELINESS'.
'creates' is the link.
(Other definitions for loneliness that I've seen before include "Solitary feeling" , "Desolation" , "Feeling of isolation" , "Unwelcome solitude" .)