Dossier parties surrendered before, essentially, Gerald Ford made it (6)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

A charade of ‘[dos]sier’ minus DOS (‘parties surrendered’) plus RA (‘essentially Ge RA ld’). The definition is puzzling: there are films entitled Sierra , High Sierra , The Treasure of the Sierra Madre etc., none of which was directed by John Ford nor starred Harrison Ford or Glenn Ford , nor involve any of them in any way. Unless I am overlooking something, I suspect a slip by Fed – perhaps most likely a confusion of John Ford with John Houston, the director of The Treasure of the Sierra Madre . A clear case of tunnel vision: SIERRA (and Ford) said film to me, and I did not look beyond that. The Ford Sierra car gives a perfectly good definition, and the surface reference to Watergate and all that makes this a truly outstanding clue.