Interior painters tell a renovator the space is astronomic (12)
I believe the answer is:
interstellar
'astronomic' is the definition.
(thesaurus)
'interior painters tell a renovator the space' is the wordplay.
'interior' says the answer is hidden in the clue (I've seen 'interior of' mean this).
'INTERSTELLAR' can be found hidden inside 'painters tell a renovator space'.
'is' is the link.
(Other definitions for interstellar that I've seen before include "In deep space" , "realm of Star Trek" , "Occurring between stars" .)