A heavenly body has to arrive on time (5)
I believe the answer is:
comet
'a heavenly body' is the definition.
(comet is a kind of heavenly body)
'to arrive on time' is the wordplay.
'to arrive' becomes 'come' (coming is a kind of arriving).
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'come'+'t'='COMET'
'has' is the link.
(Other definitions for comet that I've seen before include "Shooting star" , "high-flier" , "Heavenly visitor" , "Tailed space traveller" , "Small extraterrestrial body" .)