Graduate male -- coarse, ill-mannered person -- cut grass (6)
I believe the answer is:
bamboo
'grass' is the definition.
(I've seen this before)
'graduate male coarse ill-mannered person cut' is the wordplay.
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'male' becomes 'm' (common abbreviation).
'coarse ill-mannered person' becomes 'boor' (term for a rude person).
'cut' means to remove the last letter.
'boor' with its last letter taken off is 'boo'.
'ba'+'m'+'boo'='BAMBOO'
(Other definitions for bamboo that I've seen before include "Heavy tropical cane used in furniture" , "Woody grass plant" , "Fast-growing woody grass" , "Giant woody grass" , "'Tall, rigid grass (6)'" .)