Refers to great improvement in tobacco products (10)
I believe the answer is:
cigarettes
'tobacco products' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
I also know that 'tobacco' relates to this answer.
'refers to great improvement in' is the wordplay.
'refers to' becomes 'cites' ('cite' can be a synonym of 'refer to').
'great' becomes 'G' (abbreviation in place names).
'improvement' becomes 'aret' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'g'+'aret'='garet'
'cites' going around 'garet' is 'CIGARETTES'.
Can you help me to learn more?
(Another definition for cigarettes that I've seen is " Fags".)