Working on tiny desk with mathematical base for calculus (6,5)

I believe the answer is:

kidney stone

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'for calculus' is the definition.
(kidney stone is a kind of calculus)

'working on tiny desk with mathematical base' is the wordplay.
'working' indicates an anagram.
'with' says to put letters next to each other.
'mathematical base' becomes 'e' (Euler's number - base of natural logarithms. I am not sure about the 'mathematical' bit.).
'on'+'tiny'+'desk'='ontinydesk'
'ontinydesk' anagrammed gives 'kidneyston'.
'kidneyston'+'e'='KIDNEY-STONE'

Can you help me to learn more?

(Other definitions for kidney stone that I've seen before include "Hard mass accumulating in organ" , "Renal calculus" .)

I've seen this clue in The Telegraph.

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