Sharp accountant going over papers (4)
I believe the answer is:
acid
'sharp' is the definition.
(I've seen this before)
'accountant going over papers' is the wordplay.
'accountant' becomes 'ac'.
'going over' says to put letters next to each other.
'papers' becomes 'id' (identification papers).
'ac'+'id'='ACID'
(Other definitions for acid that I've seen before include "See 4 Across" , "scathing" , "Sour (substance)" , "Sour - type of rain or drop" , "Substance with pH of less than 7" .)