Reveal criminal's carrying iron shackles initially (7)
I believe the answer is:
confess
'reveal' is the definition.
(thesaurus)
'criminal's carrying iron shackles initially' is the wordplay.
'criminal's' becomes 'cons' (abbreviation for 'convict').
'carrying' indicates putting letters inside.
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'initially' indicates taking the first letters.
The initial letter of 'shackles' is 's'.
'cons' placed around 'fe' is 'confes'.
'confes'+'s'='CONFESS'
(Other definitions for confess that I've seen before include "Concede" , "Admit (to wrongdoing)" , "Tell a priest one's sins" , "Admit (to crime)" , "Plead guilty (in order to receive absolution?)" .)