Boy and unknown person talking on line, a seeker of romance (4,10)
I believe the answer is:
lady chatterley
'a seeker of romance' is the definition.
(character in DH Lawrence's Lady Chatterley's Lover)
'boy and unknown person talking on line' is the wordplay.
'boy' becomes 'lad' (lad is a kind of boy).
'and' says to put letters next to each other.
'unknown' becomes 'y' (algebra).
'person talking' becomes 'chatter' (a person chatting).
'on line' becomes 'ley' (as in ley lines. I am not sure about the 'on' bit.).
'lad'+'y'+'chatter'+'ley'='LADY CHATTERLEY'
(Other definitions for lady chatterley that I've seen before include "woman with inferior lover" , "Unfaithful wife" , "leading character?" , "Siren literally" .)