In time the deserter makes mistakes (6)
I believe the answer is:
errata
'mistakes' is the definition.
(erratum is a kind of mistake)
'in time the deserter' is the wordplay.
'in' means one lot of letters goes inside another.
'time' becomes 'era' (I've seen this before).
'the deserter' becomes 'rat' (I've seen this before).
'era' enclosing 'rat' is 'ERRATA'.
'makes' is the link.
(Other definitions for errata that I've seen before include "Misprints in a book" , "Listed errors" , "Printing corrections" , "mistakes in print" , "Mistakes in printed matter" .)