Villain's welcome (4)
I believe the answer is:
hiss
'villain's welcome' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hiss that I've seen before include "Make sibilant sound of disapproval as at villain" , "Show disapproval" , "Sharp sibilant sound" , "less welcome sign?" , "Sound of escaping gas" .)