Hard breaking into defenceless safe (8)
I believe the answer is:
unharmed
'safe' is the definition.
(thesaurus)
'hard breaking into defenceless' is the wordplay.
'hard' becomes 'h'.
'breaking into' is an insertion indicator.
'defenceless' becomes 'unarmed' ('unarmed' can be similar in meaning to 'defenceless').
'h' inserted inside 'unarmed' is 'UNHARMED'.
(Other definitions for unharmed that I've seen before include "Not injured or damaged" , "not wounded" .)