Inspection as unusual deficit is tackled at first (5)
I believe the answer is:
audit
'inspection' is the definition.
(I've seen this before)
'as unusual deficit is tackled at first' is the wordplay.
'at first' says to take the initial letters.
The first letters of 'as unusual deficit is tackled' is 'AUDIT'.
(Other definitions for audit that I've seen before include "Examine accounts" , "special ale" , "review of books" , "Inspection of a company's books" , "Inspection of the account books" .)