Korean · Pronunciation Guide
cha. One syllable: an aspirated ㅊ with a real burst of air, over a wide open ㅏ.
cha
A single beat, and a short one once the aspiration is out of the way. Since the word is one syllable, that breath is the only cue a listener has, which makes it worth slightly over-doing while you learn it.
Listen: 차
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제 차는 아주 작아요.
Je chaneun aju jagayo.
My car is very small.
Listen: 제 차는 아주 작아요.
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제 차는 아주 작아요 attaches the topic particle and finishes with 작아요, where the trapped ㄱ of 작 resyllabifies forward and voices, so the adjective comes out ja-ga-yo.
Softening the consonant gives 자, and there is no other cue to fall back on in a one-syllable word, so push real breath through it. Note also that 차 covers both car and tea, which are separate words in origin but identical in sound -- context does the disambiguating, not pronunciation.