Fetid coloured liquid entering wound (8)
I believe the answer is:
stinking
'fetid' is the definition.
('stinking' can be a synonym of 'fetid')
'coloured liquid entering wound' is the wordplay.
'coloured liquid' becomes 'ink'.
'entering' indicates putting letters inside.
'wound' becomes 'sting'.
'ink' inserted within 'sting' is 'STINKING'.
(Other definitions for stinking that I've seen before include "obnoxious" , "Rank" , "Foul-smelling" , "rotten!" , "smelly" .)