Leave, concerned with spilt blood (4)
I believe the answer is:
gore
'spilt blood' is the definition.
(gore is shed or spilt blood)
'leave concerned with' is the wordplay.
'leave' becomes 'go'.
'concerned with' becomes 're' (re can mean regarding, concerning).
'go'+'re'='GORE'
(Other definitions for gore that I've seen before include "Result of bleeding" , "Blood that's been shed" , "Pierce with horn - blood" , "Make a hole in" , "Pierce or wound with a horn or tusk" .)