Sound heard every second? (4)
I believe the answer is:
tick
This clue might be a double definition.
'sound' is the first definition.
(I know that tick is a type of sound)
'heard every second?' is the second definition.
'tick' can be an answer for 'second?' (both can mean a very short amount of time). I'm not sure about the 'heard every' bit.
Can you help me to learn more?
(Other definitions for tick that I've seen before include "credit > check" , "Credit; insect" , "Make noise like old clock" , "Blood-sucking arachnid" , "Instant - credit" .)