Heavenly body that rises with the sun? (7)
I believe the answer is:
mercury
This clue is a double definition.
'heavenly body' is the first definition.
(Mercury is an example)
'that rises with the sun?' is the second definition.
(as in mercury rising in a thermometer)
(Other definitions for mercury that I've seen before include "Planet next to the sun" , "Quicksilver" , "one in distant orbit?" , "Element, symbol Hg" , "Planet - rising with temperature?" .)