Admit criminal with iron shackles, gutted (7)
I believe the answer is:
confess
'admit' is the definition.
(I know that confess is a more specific form of the action admit)
'criminal with iron shackles gutted' is the wordplay.
'criminal' becomes 'con' (abbreviation for 'convict').
'with' is a charade indicator (letters next to each other).
'iron' becomes 'fe' (chemical symbol for iron).
'gutted' means to remove the middle letters (to gut something is to remove its insides).
'shackles' with its centre removed is 'ss'.
'con'+'fe'+'ss'='CONFESS'
(Other definitions for confess that I've seen before include "Admit (to crime)" , "Concede" , "Plead guilty (in order to receive absolution?)" , "Admit (to wrongdoing)" , "Tell a priest one's sins" .)