Hi,
Do you imply that there are a slight diferent value between clear up my doubt and confusion?
If I may, I'd like to make a comment about 'doubt', because the word is used a lot by learners in the Forum in a way that doesn't seem quite correct.
It's true that 'doubt' can mean a feeling of uncertainty. However, it commonly suggests what my dictionary calls 'an inclination to disbelieve'. In other words, a doubt is not simply a question. In general terms, it refers to a situation where you have an answer available, but you don't feel confident that it is the right answer. Let's consider a couple of simple non-grammar-related examples.
Wrong use - I have a doubt. Is Mary married? This is not a doubt. It's a question.
Right use - I have a doubt. Everyone tells me that Mary is married, but I think maybe she isn't. Here, you have told me the answer that you are inclined to disbelieve.
Now let's consider a typical post about grammar. Please help me. I have a doubt. Is 'table' a countable noun? This is not a doubt. It's a question.
Please help me. I have a doubt. My friends all tell me that 'table' is a countable noun, but I don't think it is. This correctly describes a doubt.
( In practice, instead of 'I have a doubt', we tend to say things like 'I have some doubt(s) about that' or 'I doubt that'. )
Best wishes, Clive