Passed on content from revolutionary walkie-talkies (4)
I believe the answer is:
Here is my best explanation:
'passed on' is the definition.
(both can mean dead)
'from revolutionary walkie-talkies' is the subsidiary indication.
'revolutionary' shows that the letters should be reversed in order.
'from' indicates the answer is hidden within the clue.
'etal' is hidden within 'walkie talkies'.
'etal' back-to-front is 'late'.
'content' is the link.
This may not be correct. It may belong to another bit of the clue.
(Other definitions for late that I've seen before include "Dead or behind time", "Yet to arrive?", "Dead or dilatory", "behind schedule", "Recently dead", "on time? No!", "Dead - tardy", "Having bought it", "Departed - behind time" and "Running behind time".)