Stellar location with Mars shot (12)
I believe the answer is:
astronomical
'stellar' is the definition.
(thesaurus)
'location with mars shot' is the wordplay.
'with' is a charade indicator (letters next to each other).
'shot' indicates anagramming the letters.
'location' put after 'mars' is 'marslocation'.
'marslocation' is an anagram of 'ASTRONOMICAL'.
(Other definitions for astronomical that I've seen before include "Really, really big" , "Of the study of stars" , "Absolutely huge, in a heavenly way" , "Massive" , "Tremendous" .)