initially i thought that the trainee should figure out their own way, showing that he can work independently without consulting seniors, but on second thought, will my answer then reflect that I'm afraid to raise issues when they arise, or that i lack communication skills?
There is an element of trying to work things out or complete the work independently, but ultimately within a law firm a lot of that will still require to check in with someone else. The bit that stands out to me is
"You have a fair idea of what to do but you are a little confused by one of the parts of the task" this suggests its not going to be efficient for you to work it out completely independently and that ultimately you are just going to work longer to try and get to a conclusion, and even then there is a significant risk how you have interpreted the task is wrong.
To me, I think it would be far better to try and speak to a supervisor/colleague to bounce ideas off of them before attempting to do the work because there is a significant risk you do it incorrectly.
Partners still check in with their colleagues and discuss idea/approaches with them to ensure they are efficient with their time (which then helps them charge out more hours to clients) and to reduce risks of getting things wrong. And that's really what is important in this question - its not you or the partner, its whether the work you are doing will benefit a client and help retain/build a relationship with them.