Would you please tell me what these expressions mean ?
1) As an apprentice, queuing in the spotless corridor on Thursdays outside the wages window, peering in at the comparative purity of desks and paper and slick, dandified staff, you got a queer, dizzy sensation. My brother was a clerk himself, at the Council House, but I never connected him with this Thursday vision.
wages window = the window through which the worker was paid his/her wages
The narrator has not connected his brother with this weekly process of receiving payment through the window.
2) Another clerical job, at a builder’s merchants, was redeemed to some extent by the fact that you were actually in the warehouse, among storemen, sales reps, and all the tangible, fascinating paraphernalia of the trade...
a company supplying builders with what they require to carry out their work.
3) an established clerk
A clerk whose position is assured.