A sign car vacated garage earlier on (6)
I believe the answer is:
gemini
'a sign' is the definition.
(Gemini is a star sign)
'car vacated garage earlier on' is the wordplay.
'car' becomes 'mini' (Mini Cooper).
'vacated' says to hollow out the word (remove centre letters) (internal letters vacate the word).
'earlier on' is a charade indicator (letters next to each other).
'garage' with its centre taken out is 'ge'.
'mini' after 'ge' is 'GEMINI'.
(Other definitions for gemini that I've seen before include "set of twinklers" , "Castor and Pollux constellation" , "Twins constellation" , "Third zodiacal sign" , "lot of stars" .)