Mother holding headgear for religious sage (7)
I believe the answer is:
mahatma
'religious sage' is the definition.
'mother holding headgear' is the wordplay.
'mother' becomes 'mama' (mama is a kind of mother**).
'holding' means one lot of letters goes inside another.
'headgear' becomes 'hat' (hat is a kind of headgear).
'mama' enclosing 'hat' is 'MAHATMA'.
'for' acts as a link.
(Other definitions for mahatma that I've seen before include "Great Soul, as Gandhi was called" , "Sage (as e.g. Gandhi)" , "Gandhi, for example" , "Wise and holy leader in 12" , "(Indian) holy person or sage" .)