Say how stars are made, out East (6)
I believe the answer is:
assert
'say' is the definition.
(thesaurus)
'stars are made out east' is the wordplay.
'are made' is an anagram indicator.
'out' means one lot of letters goes inside another.
'east' becomes 'e' ('E' can be a synonym of 'east').
'stars' is an anagram of 'assrt'.
'assrt' placed around 'e' is 'ASSERT'.
'how' acts as a link.
(Other definitions for assert that I've seen before include "Aver, declare" , "Swear" , "State categorically" , "State firmly and positively" , "Forcefully state" .)