Upsetting me, insane to go round? Hard cheese (9)
I believe the answer is:
emmenthal
'cheese' is the definition.
(Emmenthal is an example)
'upsetting me insane to go round? hard' is the wordplay.
'upsetting' shows that the letters should be reversed in order.
'insane' becomes 'mental' (I can't justify this - if you can you should give a lot more credence to this answer).
'to go round?' is an insertion indicator.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'me' back-to-front is 'em'.
'mental' enclosing 'h' is 'menthal'.
'em'+'menthal'='EMMENTHAL'
Can you help me to learn more?
(Other definitions for emmenthal that I've seen before include "Type of cheese" , "Swiss valley giving its name to a cheese" , "Something cheesy" , "Swiss cheese with holes" , "Hard Swiss cheese" .)