Beastly female going to Balmoral? I couldn’t care less! (2,4)
I believe the answer is:
so what
'i couldn't care less' is the definition.
(I've seen this before)
'beastly female going to balmoral?' is the wordplay.
'beastly female' becomes 'sow' (female pig).
'going to' means one lot of letters go next to another.
'balmoral?' becomes 'hat' (Type of head covering).
'sow'+'hat'='SO WHAT?'
(Other definitions for so what that I've seen before include "is that surprising?" , "I'm not interested" , "Big deal!" , "Expresses contempt or lack of interest" , "I couldn't care less" .)