The most common and most likely answer to this crossword clue is the 8 letter word TRANSMIT
I've seen this crossword clue in The Times
T
R
A
N
S
M
I
T
More clues leading to the result TRANSMIT
- Broadcast Martin's arranged on time
- I must leave schools with German radio
- Broadcast mike in a van
- Pass on Sumatran’s mitre box
- Pass on characteristic involving, primarily, nose, skull and mouth
- Mike installed inside carriage for broadcast
- Broadcast shows monarch’s head in carriage
- Broadcast managed to fill times on vacation with German
- Send Tristan the wrong way round motorway
- Male in carriage is forward
Buddy explains!

The straight part
We know that "radio" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case radio = transmit.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TRANSMIT mean?
TRANSMIT verb- To send or convey something from one person, place or thing to another.
- To spread or pass on something such as a disease or a signal.
- To impart, convey or hand down something by inheritance or heredity.
- To communicate news or information.
- To convey energy or force through a mechanism or medium.
- To send out a signal (as opposed to receive).