Calculating crime that I arranged (10)
I believe the answer is:
arithmetic
'calculating' is the definition.
(I've seen this before)
'crime that i arranged' is the wordplay.
'arranged' indicates an anagram (letters rearranged).
'crime'+'that'+'i'='crimethati'
'crimethati' anagrammed gives 'ARITHMETIC'.
(Other definitions for arithmetic that I've seen before include "kind of mean" , "summing up maybe" , "School subject" , "One of the three R's" , "manipulation of figures" .)