Irritating sound Telstra corrected with seconds to go (6)
I believe the answer is:
rattle
'irritating sound' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rattle that I've seen before include "Warning given by deadly snake" , "American viper" , "Child's toy; unsettle" , "Make nervous; child's toy" , "American snake" .)