In morning Naomi lively, a gas! (7)
I believe the answer is:
ammonia
'a gas' is the definition.
(ammonia is a kind of gas)
'in morning naomi lively' is the wordplay.
'in morning' becomes 'am' (as in 12:00 AM. I am not sure about the 'in' bit.).
'lively' indicates an anagram (letters get livened up or moved around).
'naomi' anagrammed gives 'monia'.
'am'+'monia'='AMMONIA'
Can you help me to learn more?
(Other definitions for ammonia that I've seen before include "Pungent cleaning fluid" , "pungent chemical" , "Pungent gas used in cleaning liquids" , "Colourless gas with strong smell" , "compound?" .)