Messenger finds a new set (5)
I believe the answer is:
angel
'messenger' is the definition.
(heavenly messenger)
'a new set' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'set' becomes 'gel' (both can mean to harden).
'a'+'n'+'gel'='ANGEL'
'finds' acts as a link.
(Other definitions for angel that I've seen before include "Messenger of God" , "Christmas tree decoration" , "eg Gabriel" , "One backing plays" , "Messenger < is a nurse" .)