Rhythmical lines to convey right sort of literary introduction (5)
I believe the answer is:
proem
'sort of literary introduction' is the definition.
(type of introduction to a piece of writing)
'rhythmical lines to convey right' is the wordplay.
'rhythmical lines' becomes 'poem' (**).
'to convey' means one lot of letters goes inside another (convey can mean to carry).
'right' becomes 'r' (common abbreviation).
'poem' enclosing 'r' is 'PROEM'.
(Other definitions for proem that I've seen before include "introduction" , "introductory piece" , "Prelude" , "Preliminary part" .)