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 a hidden word (some 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" .)