There are four entries that refer the four classic elements. EARTH; WATER; AIR; and FIRE. Each such entry has as secondary clue that refers to a word of phrase that is formed by the three entries in that line: unEARTHed; noW AT ERst; impAIRment; and bonFIRE night.
5D refers to a "removed clue". And quintessence and quintessential derive from and literally mean, the concept of a "Fifth Element".
So..... The removed clue that is not included in this grid would be: FIFTH ELEMENT; Disease prevention by DNA modification. And there'd be a row of entries that along with the name of the fifth element would answer the clue "Disease prevention by DNA modification".
In the center row we have entries GEN and APY with a row of five blank spaces. If we insert the name of the Fifth Element into it we get:
genE THERapy.
ETHER (or Aether) is the fifth element in classical Greek philosophy and therefore the answer to the meta.