American space explorer models sun with Kepler (9)
I believe the answer is:
spelunker
'american space explorer' is the definition.
(primarily US term for a cave explorer)
'models sun with kepler' is the wordplay.
'models' indicates an anagram.
'with' means one lot of letters go next to another.
'sun' put after 'kepler' is 'keplersun'.
'keplersun' anagrammed gives 'SPELUNKER'.
(Other definitions for spelunker that I've seen before include "caver" , "Chambers I explore" , "whizz in a chamber" .)