Stab some colleagues spitefully? (5)
I believe the answer is:
guess
'stab' is the definition.
(I have seen 'A stab' mean 'guess' so perhaps 'stab' could also mean 'guess')
'some colleagues spitefully?' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'GUESS' is hidden in the letters of 'colleagues spitefully'.
(Other definitions for guess that I've seen before include "Speculate" , "Reckon" , "Hypothesis" , "Imagine" , "Estimate; suppose" .)