The scene is very physical, with the drumbeat becoming a part of the people's bodies and with its focus on a wrestling contest. But this scene also emphasizes a collective spirit that enjoys organized displays of strength.
The crowd had surrounded and swallowed up the drummers, whose frantic rhythm was no longer a mere disembodied sound but the very heartbeat of the people.
slender stem-like structure by which some twining plants attach themselves to an object for support
Note how Ikemefuna is being compared to a yam and to sap. This emphasizes the agricultural way of life in Umuofia. It also makes Ikemefuna seem more tragic because he didn't live through enough seasons to ripen as a man's crop or to wither like a tree.
He grew rapidly like a yam tendril in the rainy season, and was full of the sap of life.
Nwoye knew that it was right to be masculine and to be violent, but somehow he still preferred the stories that his mother used to tell, and which she no doubt still told to her younger children—stories of the tortoise and his wily ways, and of the bird eneke-nti-oba who challenged the whole world to a wrestling contest and was finally thrown by the cat.
He remembered the story she often told of the quarrel between Earth and Sky long ago, and how Sky withheld rain for seven years, until crops withered and the dead could not be buried because the hoes broke on the stony Earth.
something that precedes and indicates the approach of something or someone
The pronoun "they" refers to a small swarm of locusts that arrives before the mass of locusts descends like a black cloud that covers half the sky. In the Bible, the descent of locusts was seen as a plague; here, they're seen as a rare opportunity for tasty treats. Later, when a couple of missionaries come as harbingers of British colonists, the villagers' reactions to them are a mix of both views.
Using "succulent" to describe a woman's breasts seems sexually inappropriate but it isn't here because 1) Akueke is showing off her body to get a better bride-price for her family; 2) it confirms that Akueke is ripe for her future duties as a wife and mother; 3) it contrasts with the sexually inappropriate staring of Marlow at Kurtz's African woman whom he describes as "savage and superb" (in Conrad's Heart of Darkness)
She wore a black necklace which hung down in three coils just above her full, succulent breasts.
"Glory" could also mean "a state of high honor", which a woman who produces many sons for her husband would have. "Crowning glory" could refer to the moment the baby's head crowns and the mother is rejoicing that her painful labor is nearly over and she'd be rewarded with the gift of life; it could also refer to the halo around a saint's head (although Ekwefi is not Christian, Achebe is, and in the novel, "Mother is Supreme.")
The birth of her children, which should be a woman's crowning glory, became for Ekwefi mere physical agony devoid of promise.