Sequence essentially replaced by binary digit for Telstar? (7)
I believe the answer is:
orbiter
'sequence essentially replaced by binary' is the definition.
I know nothing about this answer so I can't tell whether this works.
'digit for telstar?' is the wordplay.
I cannot quite see how this works, but
'digit' could be 'bit' (I have seen 'Binary digit ' mean 'bit' so perhaps 'digit' could also mean 'bit') and 'bit' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for orbiter that I've seen before include "Craft going round planet" , "One goes round" , "Circling spacecraft" , "Non-landing spacecraft" , "Satellite perhaps" .)