Waves that are flash cars (7)

I believe the answer is:

rollers

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This might be a double definition.

'waves that are flash' is the first definition.
'rollers' can be an answer for 'waves' (roller is a kind of wave). I am not sure about the rest of the definition.

'cars' is the second definition.
(I have seen 'expensive cars' mean 'rollers' so perhaps 'cars' could also mean 'rollers')

Can you help me to learn more?

(Other definitions for rollers that I've seen before include "Long heavy sea waves" , "expensive cars" , "They may be used to paint" .)

I've seen this clue in the Sydney Morning Herald.

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