Serious listener - north-east saint (7)
I believe the answer is:
earnest
'serious' is the definition.
(similar in meaning)
'listener north-east saint' is the wordplay.
'listener' becomes 'ear' (body part which hears or listens).
'north east' becomes 'ne'.
'saint' becomes 'st' (abbreviation).
'ear'+'ne'+'st'='EARNEST'
(Other definitions for earnest that I've seen before include "Nearest (anag.)" , "art collector" , "promise" , "Showing sincere and intense conviction" , "Eastern (anag.)" .)