Time to attack endlessly unfair work conditions (4,4)
I believe the answer is:
zero hour
'time to attack' is the definition.
(I've seen this before)
'endlessly unfair work conditions' is the wordplay.
'endlessly' means to remove the last letter.
'unfair work conditions' becomes 'zerohours' (as in zero hours contracts).
'zerohours' with its final letter taken off is 'ZERO HOUR'.
(Other definitions for zero hour that I've seen before include "Kick-off" , "Time for take-off" , "Midnight" , "set to start the action?" , "when attack begins?" .)