Stay again, with mother, in (6)
I believe the answer is:
remain
'stay' is the definition.
('remain' can be a synonym of 'stay')
'again with mother in' is the wordplay.
'again' becomes 're'.
'with' says to put letters next to each other.
'mother' becomes 'ma' (ma is a kind of mother).
're'+'ma'+'in'='REMAIN'
(Other definitions for remain that I've seen before include "Stay (in position)" , "Survive" , "Stay around" , "Marine (anag)" , "stop behind?" .)