I like Inquisitors; solving them usually teaches me something. This one was no exception; I did not know that the Brownies were known as the Rosebuds until 1915. In this one, the rubric did not look too scary:
Clashes in a small number of cells must be resolved, and the central square filled, to display a prominent 25 associated a century ago with the name at 6ac. The revised name, adopted the following year, must be entered in the blank space at 40, forming new words downwards. One answer is an acronym.
Not only did it not look too scary, but 25dn was clued, and CITIZEN came out fairly quickly, and when I saw WELLES down the main diagonal, and the final D in 6 across from DOTS, that gave ROSEBUD, and the clashes in the grid could be resolved to give ORSON to precede Welles, and all looks well. But! Citizen Kane was from 1941: by no stretch of the imagination was that a century ago. So, what were the other letters from the clashes? DENP. Hm. Oh, look, the first two letters on the main diagonal are BA – and BADEN-POWELL would indeed fit the preamble. And 6ac clues for ROSEBUD in both contexts. Very nice indeed. (See fifteensquared for more analysis.)
6ac: ROSEBUD: Potential peace maker?: Cryptic Definition; see above
40ac: BROWNIE (unclued)