Shed tears over one line about musical content (5)
I believe the answer is:
lyric
'musical content' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'shed tears over one line about' is the wordplay.
'shed tears' becomes 'cil' (I can't explain this - if you can you should give a lot more credence to this answer).
'over' is an insertion indicator.
'one line' becomes 'ry' (abbreviation for railway).
'about' says the letters should be written in reverse.
'cil' enclosing 'ry' is 'ciryl'.
'ciryl' back-to-front is 'LYRIC'.
Can you help me to learn more?
(Other definitions for lyric that I've seen before include "Cyril (anag.)" , "Expressing poetical emotions" , "Text of a popular song" , "Song's words" , "Of poetry that expresses thoughts and feelings" .)