Telling shifts in human interactions (13)
I believe the answer is:
relationships
'human interactions' is the definition.
'telling shifts' is the wordplay.
'telling' becomes 'relation' ('relation' can be a synonym of 'telling').
'shifts' becomes 'ships' (both can mean to transport).
'relation'+'ships'='RELATIONSHIPS'
'in' is the link.
(Other definitions for relationships that I've seen before include "Sexual liaisons" , "Connections" .)