It could be a group of outcast ninjas who have a grudge against the Hidden Leaf Village. They target Tenten as she is an easy target for them to vent their anger on. They might be jealous of the Hidden Leaf's prosperity and think by abusing Tenten, they can send a message to the village.
Well, one possible plot could be that Tenten is being held captive by some rogue ninjas who are abusing her for information. Naruto, with his strong sense of justice, discovers her situation. He uses his shadow clones to create a distraction and then swoops in to rescue her. Afterward, they form a closer bond and Naruto helps Tenten overcome the trauma of the abuse.
It could be a group of outcast ninjas who have a grudge against Konoha. They see Tenten as an easy target since she is often on solo missions or training alone. These ninjas might be using cruel and unethical methods to try and break her spirit or get some sort of advantage over Konoha.
In this fanfiction, Tenten might be in a mission where she is captured by an enemy village. They are abusing her to get information about Konoha. Naruto, who is out on a search for her, uses his shadow clones to infiltrate the enemy base. Once he finds Tenten, he battles the captors. His unwavering determination and the power of the Nine - Tails' chakra help him defeat them all. He then rescues Tenten and they make their way back to Konoha together, with Tenten being very grateful to Naruto for saving her.
Well, in fanfictions there could be various ways. He might use his Rasengan to create an opening in Gi Sensei's defenses and then rush in to save Tenten. Another possibility is that Naruto uses his speed and agility, enhanced by the Nine - Tails' chakra perhaps, to dodge Gi Sensei's attacks and reach Tenten before she gets hurt.
Sure, it's possible. Naruto has his own set of powers and a strong sense of justice. In the fanfiction world, he could see Tenten in trouble and decide to act. He might not fully understand the concept of gay fanfiction, but he doesn't need to. All he needs to do is recognize that Tenten is in a bad situation and use his abilities like the Rasengan or his ability to make friends and allies to get her out of it. It would be like one of his normal rescue missions, just in a different setting.
Naruto could use his shadow clone jutsu to create distractions. While Gai is busy dealing with the clones, Naruto can quickly get Tenten to a safe place.
In many fanfictions, Naruto might use his ninja skills. He could suddenly appear and physically stop the bullies. For example, he might use his Shadow Clone Jutsu to surround the bullies and intimidate them into leaving Sakura alone.
One possible plot could be that it's an alternate universe where Naruto and Tenten end up together in a situation that leads to pregnancy. Maybe they were on a mission together and some strange magic or jutsu affected them, causing Tenten to become pregnant. They then have to deal with the reactions of their friends and the challenges of impending parenthood.