Neverland magic. Or the croc had a taste for clocks and just ate multiple of them over the course of years.
Real wind up-up clocks only last for 10 days per wind, of accurate time keeping. It will slowly stop completely a few weeks after that, month and a half at most.
There is also the possibility that Hook simply imagined the ticking, part of a psychological phobia or post traumatic stress disorder. Nearly being killed by a giant crocodile is very traumatic, I'd imagine.
Of course, time doesn't work the same way in Never landNeverland. People don't age. Imaginary food is real and keeps them alive. A touch of Fae dust and happy thoughts make you fly. So it's not inconsistent that a Wind Upwind-up clock in neverlandNeverland never needs winding. Or HooksHook's fear of the clock keeps it ticking. It's only as real as HooksHook's mind allows it to be..