Deductions come to this positive result: catch academic at it (3,6)
I believe the answer is:
net profit
'deductions come to this positive' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'result catch academic at it' is the wordplay.
'result catch' becomes 'net' (I can't explain this - if you can you should believe this answer much more).
'academic' becomes 'prof' (short for professor).
'at' says to put letters next to each other.
'net'+'prof'+'it'='NET PROFIT'
Can you help me to learn more?
(Other definitions for net profit that I've seen before include "Actual money to be made" , "What's finally made" , "Excess of sales over costs for potent fir" , "return from business" , "Earnings after all deductions" .)