Taxingly relevant part of April (5)
I believe the answer is:
fifth
'part of april' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for fifth that I've seen before include "US amendment guaranteeing the right to silence" , "- Column is a group working for the enemy" , "20 per cent" , "Next after fourth" , "Interval of three tones and a semitone" .)