Property of informal talk on telephone (7)
I believe the answer is:
chattel
'property' is the definition.
(chattel is a kind of property)
'informal talk on telephone' is the wordplay.
'informal talk' becomes 'chat' (I've seen this before).
'on' says to put letters next to each other.
'telephone' becomes 'tel' (short for telephone).
'chat'+'tel'='CHATTEL'
'of' acts as a link.
(Other definitions for chattel that I've seen before include "Latchet (anag) - possession" , "Item of non-freehold property" , "Item of personal property" , "Movable possession" , "something one owns" .)