Skewer points upwards (4)
I believe the answer is:
spit
'skewer' is the definition.
(I know that skewer can be written as spit)
'points upwards' is the wordplay.
'points' becomes 'tips' (tip is a kind of point).
'upwards' says the letters should be written in reverse.
'tips' written backwards gives 'SPIT'.
(Other definitions for spit that I've seen before include "Metal rod for roasting meat" , "Spade-depth; rain very lightly" , "issue with some violence" , "Expectorate into pits" , "Narrow strip of land almost surrounded by water" .)