Copper, however hard, got upset (7)

I believe the answer is:
washtub
'copper' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'however hard got upset' is the wordplay.
'however' becomes 'but' (I've seen this before).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'got' becomes 'saw' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'upset' shows that the letters should be reversed in order.
'but'+'h'+'saw'='buthsaw'
'buthsaw' written backwards gives 'WASHTUB'.
Can you help me to learn more?
(Other definitions for washtub that I've seen before include "Laundry room item" , "Laundering container" , "Laundry vessel" , "Copper l" , "Bath" .)
