Ring, where that woman enters fight (6)
I believe the answer is:
washer
'ring' is the definition.
(I've seen this before)
'that woman enters fight' is the wordplay.
'that woman' becomes 'she' (she refers to a woman).
'enters' is an insertion indicator.
'fight' becomes 'war' (warring is a kind of fighting).
'she' going into 'war' is 'WASHER'.
'where' acts as a link.
(Other definitions for washer that I've seen before include "Rendered sightless" , "Baptist" , "Ring under a nut" , "Leak-stopping ring" , "Laundress" .)