Time to question Labour (4)
I believe the answer is:
task
'labour' is the definition.
(both can mean a chore)
'time to question' is the wordplay.
'time' becomes 't' (abbreviation).
'to question' becomes 'ask' (asking a question).
't'+'ask'='TASK'
(Other definitions for task that I've seen before include "Arduous bit of work" , "Burden with work" , "Piece of work to be done" , "Difficult piece of work" , "Chore, job." .)