& 3 Down Field of research that could produce essential ceramic (9)
I believe the answer is:
materials
'3 down field of research that could' is the definition.
Although both the answer and '3' are nouns, they are not in the same form of the noun.
'essential ceramic' is the wordplay.
'essential' becomes 'material' (I've seen this before).
'ceramic' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'material'+'s'='MATERIALS'
'produce' acts as a link.
Can you help me to learn more?
(Other definitions for materials that I've seen before include "Items needed to tackle a job" , "textiles" , "See 10" , "Substances that go into the making something" .)