In Axie Arena, you need to be able to withstand the first three strikes against your axie. You do this with high HP and/or high Shield part moves (Green Shield Icon on card). Examples of tanks can be found here, they likely incorporate synergy beyond a basic pure tank. The most basic pure tank is a plant or possibly aquatic axie, has no special support moves other than self heal or block attack or critical, minimal attack, high shield part moves (90+) and high axie HealthPoints (health stat over 45).You will need one of these on your team of three axies.
Click Below to see specific examples