Had to worry about sound of vehicle? (10)

I believe the answer is:

roadworthy

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'sound of vehicle?' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?

'had to worry about' is the wordplay.
'about' indicates anagramming the letters.
'had'+'to'+'worry'='hadtoworry'
'hadtoworry' is an anagram of 'ROADWORTHY'.

Can you help me to learn more?

(Other definitions for roadworthy that I've seen before include "Safe to be driven" , "fit for the journey?" , "fit to drive" .)

I've seen this clue in The Times and The Sunday Times.

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