Sage: perhaps I'm a harsh one (9)
I believe the answer is:
maharishi
'sage' is the definition.
(I've seen this before)
'perhaps i'm a harsh one' is the wordplay.
'perhaps' indicates an anagram.
'one' becomes 'I' (Roman numeral).
'im'+'a'+'harsh'='imaharsh'
'imaharsh' with letters rearranged gives 'maharish'.
'maharish'+'i'='MAHARISHI'
(Other definitions for maharishi that I've seen before include "Hindu instructor" , "Seasoned beef-pork sausage" , "Religious leader" , "Hindu spiritual leader" , "Indian sage" .)