In various nouns, one discovers a certain togetherness (6)
I believe the answer is:
unison
'togetherness' is the definition.
(being united or together)
'in various nouns one discovers a certain' is the wordplay.
'in' indicates putting letters inside.
'various' is an anagram indicator.
'one discovers' says to take the centre (I've seen 'discovered' mean this (dis-covered - outer letters removed)).
'a certain' becomes 'decided' (I've seen this in another clue).
The middle of 'decided' is 'i'.
'nouns' is an anagram of 'unson'.
'unson' enclosing 'i' is 'UNISON'.
(Other definitions for unison that I've seen before include "Concord; with same pitch" , "State of corresponding exactly; occurring together" , "A coincidence of musical notes" , "Concordance" , "Total agreement or concord" .)