In short, knowledge of no account? (3)
I believe the answer is:
esp
'account?' 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?
'in short knowledge of no' is the wordplay.
'in short' means to remove the last letter.
'knowledge' becomes 'EE' (EE is an example).
'of no' becomes 'sp' (I am not sure about this - if you are sure you should believe this answer much more).
'ee' with its final letter taken away is 'e'.
'e'+'sp'='ESP'
Can you help me to learn more?
(Other definitions for esp that I've seen before include "Extrasensory perception (abbrev.)" , "Apparent power to perceive things that others can't, in short" , "Apparent power to perceive things that others can't, initially" , "Initially, clairvoyance or telepathy" , "Second sight (abbr)" .)