Hindu instructor - mother cut his hair (9)
I believe the answer is:
maharishi
'hindu instructor' is the definition.
(I've seen this before)
'mother cut his hair' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'cut' is an anagram indicator.
'his'+'hair'='hishair'
'hishair' anagrammed gives 'harishi'.
'ma'+'harishi'='MAHARISHI'
(Other definitions for maharishi that I've seen before include "Hindu instructor" , "Teacher of Hindu mysticism" , "leading teacher" , "Seasoned beef-pork sausage" , "Hindu spiritual leader" .)