Stopped making deductions in error (12)
I believe the answer is:
discontinued
'stopped' is the definition.
('discontinue' can be a synonym of 'stop')
'deductions in error' is the wordplay.
'error' indicates anagramming the letters.
'deductions'+'in'='deductionsin'
'deductionsin' with letters rearranged gives 'DISCONTINUED'.
'making' acts as a link.
(Other definitions for discontinued that I've seen before include "No longer produced" , "Stopped" .)