They’ve done wrong by accepting the last tenders (9)
I believe the answer is:
offenders
'they've done wrong' is the definition.
I can't judge whether this definition defines the answer.
'accepting the last tenders' is the wordplay.
'accepting' is an insertion indicator (inserted letters are accepted).
'the last' becomes 'end' (I've seen this in another clue).
'tenders' becomes 'offers' ('offer' can be a synonym of 'tender').
'end' going inside 'offers' is 'OFFENDERS'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for offenders that I've seen before include "Perhaps thieves" , "Miscreants" , "They break the law" , "Lawbreakers" , "Criminals" .)