I think it is deciduous so losing its leaves at this time of year is normal.

I take it you're referring to an indoor ficus, in other words, a houseplant? They hate draughts and changes in temperature - at this time of year, they often drop leaves,( and again in the spring/early summer) and it usually means you've put your heating on, or the temperature's dropped overnight, or got hotter during the day, or it's been windy and it's catching the draught from a window. Make sure it's in a position away from a heat source, not in line of a draught from any window or door, and gets bright light - let the compost dry out slightly between waterings, and then water well, but don't leave it sitting in water for longer than half an hour. You can also add some Baby Bio houseplant food to the water fortnightly, diluted as recommended on the bottle. If you can supply all those conditions, it should settle down again.

yes silly me it is a houseplant. quite correct bamboo.