Bed American woman (6)
I believe the answer is:
bertha
'woman' is the definition.
'bed american' is the wordplay.
'bed' becomes 'berth' (berth is a kind of bed).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'berth'+'a'='BERTHA'
(Other definitions for bertha that I've seen before include "43-ton German howitzer, Big _____" , "Big girl" , "Woman's name" , "Big - - , WW1 gun" , "Big ..., heavy German howitzer in World War 1" .)