We must leave raunchy actress, right old genius (7)
I believe the answer is:
maestro
'genius' is the definition.
(thesaurus)
'we must leave raunchy actress right old' is the wordplay.
'must leave' suggests deleting specific letters.
'raunchy actress' becomes 'maewest' (actress Mae West).
'right' becomes 'r' (common abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'maewest' with 'we' taken out is 'maest'.
'maest'+'r'+'o'='MAESTRO'
(Other definitions for maestro that I've seen before include "Noted conductor" , "hotshot" , "Outstanding performer" , "Gifted performer" , "An artist of consummate skill, master" .)