Sincere listener finds cosy spot (7)
I believe the answer is:
earnest
'sincere' is the definition.
(I know that sincere can be written as earnest)
'listener finds cosy spot' is the wordplay.
'listener' becomes 'ear' (body part which hears or listens).
'finds' says to put letters next to each other.
'cosy spot' becomes 'nest' (I can't justify this - if you can you should believe this answer much more).
'ear'+'nest'='EARNEST'
Can you help me to learn more?
(Other definitions for earnest that I've seen before include "Fervent - down payment" , "Determined - heartfelt" , "Impassioned" , "Serious; down-payment" , "Intensely serious; token" .)