Star magi could finally see rising (4)
I believe the answer is:
idol
'star' is the definition.
(idol is a kind of star)
'magi could finally see rising' is the wordplay.
'finally' says to take the final letters.
'see' becomes 'lo' (archaic exclamation meaning 'look!').
'rising' says the letters should be written in reverse (in a down clue, letters go up).
The last letters of 'magi could' are 'id'.
'lo' written backwards gives 'ol'.
'id'+'ol'='IDOL'
(Other definitions for idol that I've seen before include "Object of worship (or love?)" , "Figure of worship" , "Worshipped image; lido (anag.)" , "Worshipped statue" , "Object of excessive adoration" .)