The difference between clerkship and clerk-house is maybe not a big one. To me though a clerkship would indicate a practical sort of apprenticeship and would be about Crowley teaching. That would seem to fit well with the following lines. A clerk-house seems a more administrative endeavour.
I'm wondering if the different letter totals point to something.
With clerk-house included there are 65 letters in this verse.
If we substitute clerkship then there are only 64 letters.
The word clerk-house might mean the body of Crowley's teaching up to
5°=6□. In this sense the house might be the whole system for attaining to 65 - LVX, ADNI, K&C, etc. But the actual process, the
clerkship, is one of re-Adjustment and re-balance. Oddly enough 64 is DIN, Justice.
The aspirant to any grade is trying to "sqaure the circle" indicated by the numbers of his/her grade. For example the Neophyte 1°=10□ is trying to find the Kether in Malkuth by putting their Malkuth in order (square). The natural consequence of this re-ordering and re-balancing is Ordeals. Putting one's ill-ordered house back in shape is sometimes a messy business. It's a bit like spring cleaning. Sometimes you just have to make even more mess before you can start putting everything back together again.
Thou shalt have danger & trouble. Ra-Hoor-Khu is with thee.