Heavenly high? (10)
I believe the answer is:
astronomic
I believe this clue is a double definition.
'heavenly' is the first definition.
(thesaurus)
'high?' is the second definition.
(as in astronomic prices)
(Other definitions for astronomic that I've seen before include "Prodigiously great" , "Sky-high (colloq.)" , "Relating to science" , "Incredibly large - so romantic (anag)" , "Immense" .)