Soppiness conveyed by one way of thinking (14)
I believe the answer is:
sentimentality
'soppiness' is the definition.
(thesaurus)
'conveyed by one way of thinking' is the wordplay.
'conveyed' becomes 'sent' (convey can mean to send or transport).
'by' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'way of thinking' becomes 'mentality' (I've seen this before).
'sent'+'i'+'mentality'='SENTIMENTALITY'
(Other definitions for sentimentality that I've seen before include "Gooey feeling" , "Slush" .)