Model auditor's more accurate report-writing mechanism? (10)
I believe the answer is:
typewriter
'report-writing mechanism?' is the definition.
(a typewriter might be used to write up a report)
'model auditor's more accurate' is the wordplay.
'model' becomes 'type' (both can mean a variety or kind).
'auditor's' indicates a 'sounds like' (homophone) clue.
'more accurate' becomes 'righter' ('right' can be similar in meaning to 'accurate').
'righter' sounds like 'writer'.
'type'+'writer'='TYPEWRITER'
(Other definitions for typewriter that I've seen before include "Hand-operated printer" , "Longest word obtainable using only the top line of a normal keyboard" , "printing machine" , "Former secretarial tool" , "Machine superseded by the word processor" .)