Mother going inside to sell axe (8)
I believe the answer is:
tomahawk
'axe' is the definition.
(I've seen this before)
'mother going inside to sell' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'going inside' means one lot of letters goes inside another.
'sell' becomes 'hawk' (hawking is a kind of selling).
'to'+'hawk'='tohawk'
'ma' put within 'tohawk' is 'TOMAHAWK'.
(Other definitions for tomahawk that I've seen before include "its strike can be fatal" , "Battle-axe" , "North American Indian hatchet" , "Brave's arm" , "Light native axe" .)