"Bringing the employer into disrepute" is like the so-called "morality clause"; vague and usually unenforceable , if only because it is so difficult to define. A contracted party must be able to understand what the particular term means and any argument arising over definition, any ambiguity, will be resolved or interpreted against the party (here the employer) seeking to enforce it: the 'contra proferentem' rule.
The term about not visiting rival clubs is only enforceable if the employer can demonstrate that doing so is detrimental to his business (i.e "reasonable"). Frankly, it's not easy to see how simply going to another club is detrimental. But, being practical, who wants to end up in a tribunal after they've been wrongly dismissed because of it, even if they win easily? It's hardly a great sacrifice to go along with it.