Newton omitted extremely wet gas (4)
I believe the answer is:
neon
'gas' is the definition.
(neon is a gas)
'newton omitted extremely wet' is the wordplay.
I cannot quite understand how this works, but
'newton' could be 'n' (synonyms) and 'n' is present in the answer.
The remaining letters 'eon' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for neon that I've seen before include "Gaseous element, in advertising signs, say" , "Brightly coloured advertising sign" , "'Chemical element, often used in lights (4)'" , "Inert gas, symbol Ne" , "Colourless gas, used in lighting" .)