There are a few different reasons for using the word "tackle" as a verb.
In American football, players on opposing teams try to tackle each other in order to gain an advantage on the field. To tackle another player is to knock him to the ground. Tackling is what makes football a dangerous sport.
He’s trying to tackle the quarterback.
The quarterback doesn’t want to be tackled.
When football players tackle each other, it looks as though they are fighting.
As a verb, "tackle" also means to do something that is difficult:
Our company has tackled many big problems in the last year.
The city is tackling a major reconstruction project.
If we tackle this situation together, we can achieve better results.
The word "tackle" also refers to fishing gear that is used when fishing:
I have many different lures in my tackle box.
Fishing tackle can be quite costly. Try to buy it used when possible.
If your tackle box gets wet inside, the metal hooks and lures might rust.