Tinker's dossier covering two days (6)
I believe the answer is:
fiddle
'tinker's' is the definition.
(thesaurus)
'dossier covering two days' is the wordplay.
'dossier' becomes 'file' (I've seen this before).
'covering' indicates putting letters inside.
'two' says to double the letters.
'days' becomes 'd'.
'd' doubled is 'dd'.
'file' enclosing 'dd' is 'FIDDLE'.
(Other definitions for fiddle that I've seen before include "The poor man's violin" , "Swindle with informal violin" , "Sham" , "Fix" , "Get by cheating, or handle aimlessly" .)