Categorised groups into different types of duty (8)
I believe the answer is:
taxation
'duty' is the definition.
(thesaurus)
'categorised groups into different types' is the wordplay.
I cannot really understand how this works, but
'groups' could be 'taxa' (taxon is a kind of group) and 'taxa' is found in the answer.
an anagram of 'into' is 'tion' which is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for taxation that I've seen before include "Revenue from levies" , "Money levied by government" , "the reason for protest in Boston" , "Levying of money by a government" , "The raising of state finances" .)