羁 is a classical/literary character rarely used alone in modern speech. It appears in compounds like 羁绊 (jī bàn, fetters/bonds) and the common phrase 不羁 (bù jī, unrestrained/uninhibited).
Net radical on top is the indexing radical — pictures a hunting or fishing net seen flat. In 羁 the net traps the horse below, giving the literal scene of a horse caught in a snare. From that capture image 羁 generalised to 'detain, restrain, bind'.
Lower-left shows leather — the material of the bridle and halter. 革 pictures an animal hide stretched flat for tanning. Together with the horse below, the bottom half writes 'leather + horse', i.e. tackling a horse with leather gear, the practical means of restraint.
Lower-right is the horse caught under the net and bridled with leather. The whole 17-stroke character is essentially a frozen tableau: 'horse + leather + net' = restraint. From that vivid image 羁 also gained the figurative sense of being tied down, unable to wander — 羁绊 'fetter, encumbrance'.
