There is no way to strip a single enchantment off an item and keep the others. Minecraft gives you one tool for removal, the grindstone, and it takes everything off at once.
Using a grindstone
Craft one from two sticks, one stone slab and two wooden planks. Put your enchanted item in either slot and take the plain version out of the result slot. You get some experience back — roughly what the enchantments were worth — and the item keeps its durability.
Two things survive a grindstone: curses. Curse of Binding and Curse of Vanishing cannot be removed this way, or any other way. An item carrying a curse carries it permanently.
Why you cannot remove just one
Enchantments are stored as a single list on the item, and the game offers no operation that edits that list selectively. If you have a pickaxe with Efficiency V and Silk Touch and you wanted Fortune instead, the answer is a second pickaxe, not surgery on the first.
This is exactly why planning before you spend levels matters. Silk Touch and Fortune exclude each other, as do the four Protections, Mending and Infinity, Depth Strider and Frost Walker, and Multishot and Piercing. Check the conflicts in the enchantment list before committing.
Getting value from a mistake
If you have enchanted something wrongly, the grindstone at least refunds part of the XP. Do it before you repair the item further, because grinding also resets the prior work penalty — a fresh, unenchanted item goes back into the anvil cheaply.
That reset is genuinely useful. An item that has been through the anvil five or six times becomes effectively unworkable; grinding it clean and starting again with a properly ordered book combine is often cheaper than pushing on.
Doing it right the second time
Work out the cheapest order for the whole set before you touch the anvil. The Minecraft enchantment calculator shows every step, the XP each one costs, and warns you before a step would become Too Expensive.