Theme or point in conversation, initially (5)
I believe the answer is:
topic
'theme' is the definition.
(I know that theme can be written as topic)
'point in conversation initially' is the wordplay.
'point' becomes 'top' (top is a kind of point).
'initially' suggests taking the first letters.
The initial letters of 'in conversation' is 'ic'.
'top'+'ic'='TOPIC'
'or' is the link.
(Other definitions for topic that I've seen before include "Content of argument" , "Question" , "one discussed" , "Matter for an argument" , "Issue (for discussion)" .)