Something cynical, essentially, concerning nations or races (6)
I believe the answer is:
ethnic
'nations or races' is the definition.
I can't tell whether this definition defines the answer.
'something cynical essentially' is the wordplay.
'something' becomes 'eth' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'essentially' means to look at the middle letters.
The centre of 'cynical' is 'nic'.
'eth'+'nic'='ETHNIC'
'concerning' acts as a link.
Can you help me to learn more?
(Other definitions for ethnic that I've seen before include "Relating to a particular racial group" , "Relating to cultural groups" , "To do with racial group or culture" , "from foreign cultures" , "Characteristic of a certain culture" .)