Alien discarded right of access for a moment (4)
I believe the answer is:
tick
'moment' is the definition.
(both can mean a very short amount of time)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tick that I've seen before include "Parasite - mark of approval" , "Credit; mark as correct" , "Not cross" , "Make sound like old clock" , "Parasitic insect or pillow casing" .)