one tuft; one lock
Used for a single tuft or lock of hair, threads, or similar thin, flexible strands gathered together.
See also: 房
one bunch; one cluster
Used for a single bunch of grapes, bananas, or a cluster of flowers or fruits growing together.
See also: 房
I bought a bunch of bananas at the supermarket.
one segment; one section
Used for one segment or section of a tangerine, orange, or similar fruit that naturally divides into parts.
See also: 房
She cut off a lock of her hair and gave it to him.
I separated the tangerine into segments and ate them one by one.
房 is the general noun for a tuft, bunch, or cluster, while 一房 specifically means 'one' such unit.
Compound of 一 (one) and 房 (tuft, bunch, cluster). The reading ひとふさ follows the native Japanese counting pattern.