They aren't all of the same nature (3)
I believe the answer is:
men
'they aren't all' is the definition.
The definition suggests an adverb but the answer is not.
'of the same nature' is the wordplay.
'of' indicates a hidden word.
'MEN' is hidden in the letters of 'same nature'.
Can you help me to learn more?
(Other definitions for men that I've seen before include "'So many ..., so many opinions'" , "Crew" , "gents" , "Chess pieces" , "Human males" .)