CO 2 's core parts enucleated for lower emissions (7)
I believe the answer is:
cowpats
'for lower emissions' is the definition.
(things emitted by 'lowers' - low can mean to moo)
'co 2 's core parts' is the wordplay.
'2 's' becomes 'w' (I can't justify this - if you can you should give a lot more credence to this answer).
'core' means to remove the middle letters (I've seen 'cored' mean this).
'parts' with its centre taken out is 'pats'.
'co'+'w'+'pats'='COWPATS'
'enucleated' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for cowpats that I've seen before include "Jersey product" , "Pieces of dung in fields" .)