Dossier about man staying sober is a fraud (6)
I believe the answer is:
fiddle
'fraud' is the definition.
(I've seen this before)
'dossier about man' is the wordplay.
'dossier' becomes 'file' (a dossier is a file or set of information).
'about' is an insertion indicator.
'man' becomes 'dd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'file' placed around 'dd' is 'FIDDLE'.
'staying sober is a' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for fiddle that I've seen before include "scrape" , "Toy - string instrument - cheat" , "Play - cheat" , "Fraudulent instrument?" , "Cheat on (e.g. expenses)" .)