A tackle is move in football (football assotiation, soccer in the USA) where one player tries to disposses the opponent of the ball by stretching one leg while sliding on the ground, thereby ideally gaining control of the ball or at least depriving the opponent of it. A tackle will be considered a foul punishable with a free kick, a penalty kick, a yellow or a red card if it is made lifting both feet of the ground, if it hits the oponent before hitting the ball or if it is made in a reckless, careless way or with excessive force. It the tackle succeeds in touching the ball before the opponent the tackling player may still be penalised if he makes unfair contact with the other player after playing the ball.
The corresponding verb in German is grätschen, the equivalent noun is Grätsche (f.) (there is even a Blutgrätsche, literay a blood tackle, for a particularly violent, irregular tackle), but in Spanish it is not so easy. As I found in this recent article by Jordi Quixano in el País a tackle is explained (not translated!) as „lanzarse al suelo para robar el esférico“, that is, throwing oneself to the ground to gain control of the ball. I am sorry, but I think it is a little more complicated than that. Another possibility would be the term hacer or cometer una entrada, which includes a tackle, but many more forms of disputing the ball as well, not all of them allowed by the rules. In football there are entradas reglamentarias and entradas antireglamentarias (the latter can include the above mentioned German blood tackle). In rugby (or american football) a tackle is translated into Spanish as placaje, but that term is not used in football. A placaje would always be considered a foul, except perhaps when the perpetrator is called Pepe and plays for Real Madrid.
French has simply borrowed the English term and uses it with complete ease: it is written tacle. That would be the easiest solution for Spanish but knowing the rules of the Real Academia de la Lengua for orthography in Spanish it would probably have to be written taquel. Well, why not? As long as it is clear what the word means...
Related concepts: Spagat, Zweikampf