Circuits almost become void (4)
I believe the answer is:
laps
'circuits' is the definition.
('lap' can be a synonym of 'circuit')
'almost become void' is the wordplay.
'almost' means to remove the last letter (almost the whole word is kept).
'become void' becomes 'lapse' (I've seen this before).
'lapse' with its last letter taken off is 'LAPS'.
(Other definitions for laps that I've seen before include "Circuits of a racetrack" , "Scoops up with the tongue" , "Pals doing rounds of the track" , "Circuits of track" , "Drinks; circuits" .)