Harangue worker after end of labour (4)
I believe the answer is:
rant
'harangue' is the definition.
(I've seen this before)
'worker after end of labour' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'after' is a charade indicator (letters next to each other).
'end of' indicates one should take the final letters.
The final letter of 'labour' is 'r'.
'ant' after 'r' is 'RANT'.
(Other definitions for rant that I've seen before include "Shout wildly at length" , "Show anger" , "Talk wildly and incoherently" , "Rail" , "Harangue, rave" .)