Deserter's caught in time, making mistakes (6)
I believe the answer is:
errata
'mistakes' is the definition.
(erratum is a kind of mistake)
'deserter's caught in time' is the wordplay.
'deserter' becomes 'rat' (I've seen this before).
'caught in' means one lot of letters goes inside another.
'time' becomes 'era' (I've seen this before).
'rat' put into 'era' is 'ERRATA'.
'making' acts as a link.
(Other definitions for errata that I've seen before include "Feeling nausea" , "Slips" , "Corrigenda" , "Mistakes in printed proofs" , "Mistakes in printed work" .)