(ひだね)

ひだね
noun
live ember; source of conflict
1. live ember, kindling fire
A small flame or glowing coal kept alive to start a new fire. Historically important before matches were available.
Keep the fire from going out.
In the old days, people carefully preserved their fire embers.
They buried the embers in the ash of the hearth to keep them until morning.
2. source of conflict, spark (of trouble)
Something that could trigger a conflict, dispute, or problem. Used figuratively to describe a latent cause of trouble.
That issue could become a source of conflict.
不満(ふまん)火種(ひだね)まだくすぶっている
The seeds of discontent are still smoldering.
The territorial dispute has remained a source of tension between the two countries for many years.

Usage

The figurative sense (source of conflict) is more common in modern usage than the literal sense. Often used with verbs like くすぶる (to smolder), (のこ) (to remain), and なる (to become).

Common collocations