Ugly desk, ugly rug, ugly practice (11)

I believe the answer is:

skulduggery

I'm a little stuck... Click here to teach me more about this clue!

'ugly practice' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'ugly desk ugly rug' is the wordplay.
'ugly' is an anagram indicator (an ugly or wrong form of the letters).
'desk'+'ugly'+'rug'='deskuglyrug'
'deskuglyrug' is an anagram of 'SKULDUGGERY'.

Can you help me to learn more?

(Other definitions for skulduggery that I've seen before include "Underhand trickery" , "underhandedness" , "Underhand behaviour" .)

I've seen this clue in The Telegraph.

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