Half-dead criminal provides justification (7)
I believe the answer is:
defence
'justification' is the definition.
(I know that defence is a type of justification)
'half-dead criminal' is the wordplay.
'half' suggests halving the letters.
'criminal' becomes 'fence' (someone who handles stolen goods).
'dead' cut in half is 'de'.
'de'+'fence'='DEFENCE'
'provides' is the link.
(Other definitions for defence that I've seen before include "Protection from danger" , "A means of protecting from attack" , "Protection; justification" , "Purpose of armed forces" , "See 12" .)