Poem included in clever sermon (5)
I believe the answer is:
verse
'poem' is the definition.
(I know that verse is a type of poem)
'included in clever sermon' is the wordplay.
'included in' indicates the answer is hidden within the clue.
'VERSE' can be found hidden inside 'clever sermon'.
(Other definitions for verse that I've seen before include "Part of a song or poem" , "Stanza; poetry" , "few lines of writing?" , "Literature in metrical form" , "Piece of poetry" .)