head in?

[goodsogi]

I always find it difficult to understand sports articles. The following is the sentence that I met.

"But it got worse for Newcastle when Joey Barton was sent off for a dodgy tackle on Alonso, leaving Lucas Leiva to head in a third to seal the win."

Is "head" a noun or a verb? And does "a third" indicate a position or time?

[Raymott]

I always find it difficult to understand sports articles. The following is the sentence that I met.

"But it got worse for Newcastle when Joey Barton was sent off for a dodgy tackle on Alonso, leaving Lucas Leiva to head in a third to seal the win."

Is "head" a noun or a verb? And does "a third" indicate a position or time?

I assume this is football/soccer. "Head" is a verb. To "head" the ball means to hit the ball with your head - since you aren't allowed to use your hands (unless you're Maradona).
Here it's used as a phrasal verb. To "head in" a ball means to head it into the net. Leiva hit the ball into the net with his head for a third goal, ensuring that that they won.