Carbon before new age not related (7)
I believe the answer is:
cognate
'related' is the definition.
(similar in meaning)
'carbon before new age not' is the wordplay.
'carbon' becomes 'c' (C is the chemical symbol for carbon).
'before' is a charade indicator (letters next to each other).
'new' is an anagram indicator.
'age'+'not'='agenot'
'agenot' anagrammed gives 'ognate'.
'c'+'ognate'='COGNATE'
(Other definitions for cognate that I've seen before include "Related, connected" , "from the same root" , "Associated" , "Affiliated" , "Related by blood" .)