Assuming you are referring to the case interview, yes you can ask for a time depending on a question you need to answer.
For example, if the question is requiring you to create a new approach/structure then it is fine, you may want to think in detail to cover all aspects.
If the question is more like a brainstorming type of question like “what can be the potential reasons for a decrease in weighted average price”, then it would be better for you not to ask for additional time as you will need to answer many questions like this during the case.
Having said that, taking time and giving a good answer is always better than not taking time and giving a poor answer.
So, you can primarily target to be master in cases and give good answers without needing additional time. During the case, if you believe that you need to take a time otherwise your answer will be poor, then I would recommend you to take your time instead of giving a poor answer.