Sister too upset with anguish protecting amphibians (13)

I believe the answer is:

tortoiseshell

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'sister too upset with anguish protecting amphibians' is the definition.
I can't judge whether this definition defines the answer.

'sister too upset with anguish' is the wordplay.
'upset' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'anguish' becomes 'hell' (hell can mean suffering or anguish).
'sister'+'too'='sistertoo'
'sistertoo' is an anagram of 'tortoises'.
'tortoises'+'hell'='TORTOISESHELL'

Can you help me to learn more?

(Other definitions for tortoiseshell that I've seen before include "Butterfly - cat" , "Butterfly - yellow-brown mottled material" , "Mottled plated ornamental substance" , "Domestic cat mottled in brownish-yellow and black" , "Ornamental material" .)

I've seen this clue in The Irish Times.

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