I vote for Steve. Clover may be a bit stronger and may have supernatural luck on her side, but even if Steve were to die, he would always respawn in this battle, so the best possible scenario for Clover is an inconclusive match, while it's fathomable that Steve could realistically and reliably win using some tactics.
Clover is usually untouchable, but even to the standards of
Inanimate Insanity, she's not theoretically absolutely untouchable. Her luck stems from what's most advantageous for her based on what she wants. If Clover wants to approach Steve in order to attack him, that means she's willingly putting herself in a position with risk involved. Gusts of wind blowing her to safety and random stuff fortunately getting launched in the way of what can harm her are useful for individual incidents of fate being bended in her favor, but those events themselves are still bound by logic, so, for example, if wind were to blow Clover out of the way of one thing, it can't simultaneously blow her out of the way of something else.
You wrote that Steve has all his gear and is aware of Clover's luck, so he would try to use tools that he would sensibly think could counter Clover's luck, rather than simply swinging a sword recklessly.
- Steve would be likely to try using blocks to build upward and then shoot enchanted arrows from there. They defy gravity, so Clover can't make them fall, and she can't reach Steve without putting herself in a vulnerable state. The arrows will most likely hit Clover eventually, since she seems unskillful, gusts of wind probably can't save her forever against fast projectiles, and the "random tropical island" location will eventually run out of birds to fly in the way Steve's shots. I often see enchanted arrows set enemies on fire, and Clover seems easy to burn, so if she got hit by just one of them, it would probably be the end for her.
- Steve could probably use splash potions to affect Clover, since the glass containers burst into gaseous magic, so they can affect Clover even without being shot accurately and they can interfere with the wind that favors Clover. If that logic is sound, then Steve could negate Clover's durability using splash potions of poison or decay.
- Steve could burn the area with flint and steel, limiting both of their movement options. This is far more advantageous for Steve than it is for Clover, since Steve would still have control over the battlefield via building and would be the source of the fire, meaning Clover would be the one required to adjust to what Steve wants. Clover would be likely to need to resort to a method of flight in this case, leaving her more vulnerable to projectiles.
The only downfall Steve could have against Clover is if Clover's luck pulls through, and she doesn't let him get his items back after defeating him once. This could be countered in some way with an Ender Chest, but Steve still would need to actually use his items for them to advantage him, and they would drop upon him dying. Steve losing his items would result in an inconclusive match, since there is nothing that Steve could do alone that Clover's luck can't counter, and Clover potentially using Steve's items to her advantage would only worsen Steve's situation. However, due to Steve being majorly more skillful than Clover, I think Steve would be successful on his first try.
