Record it on a polygraph, covering last remark (7)
I believe the answer is:
epitaph
'last remark' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'record it on a polygraph covering' is the wordplay.
'record' becomes 'ep' (abbreviation for extended play record).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'covering' means to remove the middle letters (the letters which cover the word are used).
'polygraph' with its middle removed is 'ph'.
'ep'+'it'+'a'+'ph'='EPITAPH'
Can you help me to learn more?
(Other definitions for epitaph that I've seen before include "Dead' record" , "Words written in memory of the dead" , "Memorial inscription" , "Commemorative inscription" , "Obituary" .)