DESU, just being a body who can throw out a spell even once per day, and can frontline perfectly fine (as opposed to the thieves and magic users who do their thing occasionally and then suck; the cleric is not only better armoured than a thief, but actually has better THAC0 as well), is by itself great in 1e. You will die a lot, but so do fighters, and so does anyone (though rangers are kinda bad at dying). Old D&D, up to 1e, is a numbers' game — that is, you brave the dungeon by throwing numbers of people at it, disposable NPCs and disposable PCs alike.
If you want to get a bit more mileage out of your spellcasting, however, then take note of two first-level spells in particular: Light and Command. Light has been abused enough that by 1e, "cast it on eyeballs" became an officially recognized use of the spell — so it's a pretty straightforward save-or-suck. Not in the same league as Sleep, of course, but Sleep is an outlier. Command, meanwhile, takes some creativity to use, but is also quite versatile (and in 1e, works on low-HD low-Int enemies without a save, to compensate for not working at all on creatures that can't understand or hear you). It work s particularly well if you can afford some preparations and carry various items that work well with it. I remember downing an ogre with a barrel of dwarven mead and a repeated "Drink!" Command. Good times, good times.
If your party is inclined enough to treat combat as war and avoid fair fights, you can also get some mileage out of using Putrefy food and drink (reversed version of Purify) to sabotage food supplies.
Finally, while 2e's Complete Priest's specialty priests are definitely lowballed compared to default 2e cleric or later supplements, it's that toothlessness that might help you talk your DM into allowing the book for use with 1e. If all you want is a cleric who swords, or tricksters, or charms animals (very helpful) while being a better frontliner than a druid, go for it.