Move on the subject of bloodshed (4)
I believe the answer is:
gore
'bloodshed' is the definition.
('gore' can be a synonym of 'bloodshed')
'move on the subject of' is the wordplay.
'move' becomes 'go' (going is a kind of moving**).
'on' means one lot of letters go next to another.
'the subject of' becomes 're' (I've seen this in other clues).
'go'+'re'='GORE'
(Other definitions for gore that I've seen before include "Impale" , "Pierce or wound with a horn or tusk" , "Showing guts" , "Coagulated blood from a wound" , "Blood on a piece let into a garment?" .)