Fatty things, roughly two on each of us (5)
I believe the answer is:
chips
'fatty things' is the definition.
The answer and definition can be both acts as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'roughly two on each of us' is the wordplay.
'roughly' becomes 'c' (circa).
'two on each of us' becomes 'hips' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'c'+'hips'='CHIPS'
Can you help me to learn more?
(Other definitions for chips that I've seen before include "Silicon wafers" , "Goodbye, Mr. ---; --- with Everything" , "Potato slices, good with fish" , "Gambling counters" , "fast food?" .)