Turned me mad about hard cheese (9)
I believe the answer is:
emmenthal
'cheese' is the definition.
(Emmenthal is an example)
'turned me mad about hard' is the wordplay.
'turned me' becomes 'em' (I can't justify this - if you can you should give a lot more credence to this answer).
'mad' becomes 'mental' (mentally ill).
'about' is an insertion indicator.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'mental' going around 'h' is 'menthal'.
'em'+'menthal'='EMMENTHAL'
Can you help me to learn more?
(Other definitions for emmenthal that I've seen before include "Swiss cheese with holes" , "Hard Swiss cheese" , "Something cheesy" , "Swiss valley giving its name to a cheese" , "Type of cheese" .)