Translation:What time is it?
No, it's used to indicate a long vowel sound, and though it's typically used in katakana words, it's acceptable with hiragana in casual settings.
Here, the lengthening of the "a" in "cha" is a commonly used trick in Japanese to mimic "r" sounds at the end of words (like "adventure"). It sounds reasonably close to my Australian ears, but might not be so convincing to Americans.
とき is one of the possible pronunciations (kun'yomi) of 時, and is used to describe time in a general sense (à la space-time) or as an occasion/instance (食べる時 = "when I eat", lit. "eating time").
In this case, you can think of 時 (pronounced じ) as meaning "hour", so the question is asking "what hour (of the day) is it?"