Cockney tough guys died? That’s correct (5)
I believe the answer is:
emend
'correct' is the definition.
(I've seen this before)
'cockney tough guys died?' is the wordplay.
'cockney tough guys' becomes ''emen' ('hemen' - stereotypically masculine men - said with the 'H' dropped - a cockney accent.).
'emen'+'d'='EMEND'
'that's' is the link.
(Other definitions for emend that I've seen before include "Alter something written to correct errors" , "Revise (a text) (E, not A)" , "change" , "Make correction in written material" , "Remove faults from" .)