。
I'll stand by you through thick and thin.
Literal
All-obstacles [object-を] remove [and-て], your ally [object-を] let's-do [volitional-しよう].
万難を排する ('to push aside ten-thousand difficulties') is a formal/literary set expression for overcoming all obstacles — committing to an action regardless of what stands in the way. 味方をする ('to do allyship,' 'to be on someone's side') is a set collocation. The volitional しよう ('let's do,' 'I shall do') marks personal determination.