Stars host introduction to solemn prayer (6)
I believe the answer is:
orison
'prayer' is the definition.
(I know that prayer can be written as orison)
'stars host introduction to solemn' is the wordplay.
'stars' becomes 'orion' (Orion is a constellation).
'host' indicates putting letters inside (inserted letters are hosted or welcomed).
'introduction to' suggests taking the first letters.
The initial letter of 'solemn' is 's'.
'orion' enclosing 's' is 'ORISON'.
(Other definitions for orison that I've seen before include "O, no, sir, it makes a prayer" , "Supplication" , "Prayer - O no sir! (anag)" , "An archaic or literary prayer" .)