Low female voice -- understand the woman completely (10)
I believe the answer is:
altogether
'completely' is the definition.
(I know that completely can be written as altogether)
'low female voice understand the woman' is the wordplay.
'low female voice' becomes 'alto' (I've seen this in another clue).
'understand' becomes 'get' (getting is a kind of understanding).
'the woman' becomes 'her' (her refers to a woman).
'alto'+'get'+'her'='ALTOGETHER'
(Other definitions for altogether that I've seen before include "Completely, on the whole" , "Entirely" , "special to get Hermes trousers" , "Completely, in total" , "Quite" .)