This transcendental number is pretty risqué; it's positively criminal (6)
I believe the answer is:
piracy
'positively criminal' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'this transcendental number is pretty risque' is the wordplay.
I cannot really understand how this works, but
'number' could be 'i' (I is an example) and 'i' is located in the answer.
'risque' could be 'racy' (synonyms) and 'racy' is located in the answer.
A single letter 'p' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'it's' is the link.
Can you help me to learn more?
(Other definitions for piracy that I've seen before include "Illegal copying" , "theft" , "Act of plagiarism" , "burglary, in the main?" , "Robbery at sea or of copyright" .)