For reason that follows notes (7)
I believe the answer is:
because
'for' is the definition.
(thesaurus)
'reason that follows notes' is the wordplay.
'reason' becomes 'cause' (I've seen this before).
'that follows' says to put letters next to each other.
'notes' becomes 'be'.
'cause' after 'be' is 'BECAUSE'.
(Other definitions for because that I've seen before include "Thanks to this" , "Owing to" , "For the reason that" , "On account of" , "Since" .)