Time to join messenger, old fruit (7)
I believe the answer is:
tangelo
'fruit' is the definition.
(I know that tangelo is a fruit)
'time to join messenger old' is the wordplay.
'time' becomes 't' (abbreviation).
'to join' is a charade indicator (letters next to each other).
'messenger' becomes 'angel' (heavenly messenger).
'old' becomes 'o' (abbreviation).
't'+'angel'+'o'='TANGELO'
(Other definitions for tangelo that I've seen before include "fruitful merger?" , "Hybrid fruit; eat long (anag.)" , "Mixed fruit" , "Citrus fruit hybrid" , "sharp cross" .)