Crossword Genius

Line of little dots on the radio (4)

Ross

I believe the answer is:

flex

I'm a little stuck... Click here to teach me more about this clue!

This clue could be a double definition.

'line of little dots' is the first definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?

'the radio' is the second definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'on' is the link.

Can you help me to learn more?

(Other definitions for flex that I've seen before include "Bend - electrical cable" , "Supply contract" , "Electric wire" , "Tighten - bend" , "Bend - electric cable" .)

I've seen this clue in The Independent.
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