Mother's sure about rubber (7)
I believe the answer is:
masseur
'rubber' is the definition.
(someone who rubs or massages people)
'mother's sure about' is the wordplay.
'mother's' becomes 'ma's' (ma can mean mother).
'about' is an anagram indicator.
'sure' is an anagram of 'seur'.
'mas'+'seur'='MASSEUR'
(Other definitions for masseur that I've seen before include "Parlour worker" , "One working in parlour" , "One who kneads bodies" , "Erasmus? (anag)" , "Professional rubber?" .)