This is not always straightforward and it is a complex subject. Generally the aim of the restrictive covenant is to prohibit you from competing with your ex-employer for a period of time after you would have left the business. Furthermore clauses may also include prevention from soliciting or dealing with your ex-employers customers.
A thorough understanding of your ex-employers business would be essential as well as what your next move is. The enforceability of the clause would depend on how it is drafted and whether it is designed to protect the employer’s legitimate business interest and that such clause is not beyond what is reasonably necessary to protect those interests.
However detailed advice would be required for such a matter as this can be very intricate and costly.