Taxman rehash oddly upset shrink (7)
I believe the answer is:
shrivel
'shrink' is the definition.
(I know that shrink can be written as shrivel)
'taxman rehash oddly upset' is the wordplay.
'taxman' becomes 'levi' (I can't justify this - if you can you should give a lot more credence to this answer).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'upset' says the letters should be written backwards.
The alternate letters of 'rehash' are 'rhs'.
'levi'+'rhs'='levirhs'
'levirhs' reversed gives 'SHRIVEL'.
Can you help me to learn more?
(Other definitions for shrivel that I've seen before include "Wither with loss of moisture" , "Contract into wrinkles" , "Wither, shrink" , "Dehydrate" , "Become dry and withered" .)