... maybe second set of lines found after second reading? (5,4)
I believe the answer is:
morse code
'maybe second set of lines found after second reading?' is the definition.
I can't tell whether this defines the answer.
'second set of lines found after second reading?' is the wordplay.
'second' becomes 'sec' (synonyms).
'set of lines' becomes 'ode' (ode is a type of poem).
'found after' is a charade indicator (letters next to each other).
'second' becomes 'mo' (both are short periods of time).
'reading?' becomes 'r' (one of the traditional three R's of education).
'sec'+'ode'='secode'
'mo'+'r'='mor'
'secode' after 'mor' is 'MORSE CODE'.
(Other definitions for morse code that I've seen before include "Means of communication using dots and dashes" , "Dots and dashes alphabet" , "Signalling system of dots and dashes" , "Dot-dash alphabet" , "Means to communicate" .)