Same kit reused? That’s an oversight (7)
I believe the answer is:
mistake
'an oversight' is the definition.
(I've seen this in another clue)
'same kit reused?' is the wordplay.
'reused?' indicates an anagram (I've seen 'reused' mean this).
'same'+'kit'='samekit'
'samekit' is an anagram of 'MISTAKE'.
'that's' acts as a link.
(Other definitions for mistake that I've seen before include "Slip" , "Fault" , "Error" , "Oversight" , "Wrong action or judgment" .)