Stay to put mother in control (6)
I believe the answer is:
remain
'stay' is the definition.
(I know that stay can be written as remain)
'mother in control' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'in' means one lot of letters goes inside another.
'control' becomes 'rein' (synonyms).
'ma' placed inside 'rein' is 'REMAIN'.
'to put' acts as a link.
(Other definitions for remain that I've seen before include "Stay around" , "Survive" , "Old dance" , "Stay, don't go" , "Stay (in position)" .)