noun
Refers to a small broken-off piece of something physical, or metaphorically a tiny amount of something abstract like emotion or truth.
ガラスのひとかけらが床に落ちていた。
A fragment of glass had fallen on the floor.
彼の話には真実のひとかけらもなかっ
There wasn't even a shred of truth in his story.
かけら is a more general word for 'fragment' or 'piece'. ひとかけら emphasizes a single, often small, piece and is commonly used in negative expressions like ひとかけらもない (not even a fragment).
Compound of 一 (ひと, 'one') and かけら (kakera, 'fragment'). The exact origin of かけら is uncertain, but it is a native Japanese word.