IN A BREAK with bad tradition, the District Council is actually thinking about new rent-control legislation in time to do something constructive before the current law expires.This doesn't guarantee good and timely results, but it would beat another, last-minute, head-in-the-sand extension of what's on the books now. Council Chairman Arrington Dixon is calling not only for prompt action, but also for an alternative to rent control. His courage is in marked contrast with the attitudes taken by his council colleagues.

At a committee hearing last week, Mr. Dixon correctly termed the city's law a failure and said it has not protected the poor. He would replace it with measures requiring changes in the tax laws. Under his proposals, whose details are still being crafted, lower-income tenants who pay more than 35 percent of their incomes for rent would be allowed to get tax credits. Renters could deduct some form of property tax paid to the city. And lifetime tenancies would be provided for the elderly. Mr. Dixon also would place a tax on rental units and condominium conversions; there would be a limit on the number of conversions in each of the city's eight wards.

Obviously the council needs to know more about these proposals, but Mr. Dixon's emphasis on exploring alternatives to rent controls deserves support. Tenant organizations, too, many find the alternatives more helpful to the poor than rent-control laws thank shrink the housing supply, over burden government agencies and generally aggravate an already tight market.

Even if the council moves constructively, of course, there may be another obstacle: Mayor Barry. Though Mr. Barry is said to believe that a strong rent-subsidy program could eventually replace rent-control laws, he's apparently afraid that any proposed law will become a political football if it is considered during the "supercharged" climate of council elections. That may be so, but this game has gone into overtime already. The current law expires in September. If the mayor and concerned council members would only join forces and take on the rent-control issue forth-rightly, renters and property owners in this city could be a lot better off.