Elegy involved pipe and hat (7)
I believe the answer is:
epitaph
'elegy' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'involved pipe and hat' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'and' is a charade indicator (letters next to each other).
'pipe' after 'hat' is 'hatpipe'.
'hatpipe' is an anagram of 'EPITAPH'.
Can you help me to learn more?
(Other definitions for epitaph that I've seen before include "Pit heap (anag)" , "Words carved on a gravestone" , "Words written on a gravestone" , "Words written in memory of the dead" , "Tombstone inscription" .)