Rain slightly slants to the left (4)
I believe the answer is:
spit
'rain slightly' is the definition.
(I've seen this in another clue)
'slants to the left' is the wordplay.
'slants' becomes 'tips' ('tip' can be a synonym of 'slant').
'to the left' says the letters should be written backwards (reading from right to left).
'tips' backwards is 'SPIT'.
(Other definitions for spit that I've seen before include "Show disdain" , "Rotating cooker" , "Eject saliva - roasting rod" , "Rain in scattered drops" , "turning means of 8 [COOKING]" .)