PROSTITUTION HAS MOVED in on Thomas Circle in a big way.Not that it hasn't always been with us, but now that area has turned into something of a combat zone. There's been a dramatic increase in the number of prostitutes on the street and a growing attitude that "anything goes" in Washington. Police report that there have been 20 prostitution-related murders around Thomas Circle in the past two years. Moreover, as a story in this newspaperr last week made plain, there is no obvious or perfect way to deal with this epidemic of prostitution, which brings in its wake drug traffic, assults, robberies and even murder.

Those who work and live in the Thomas Circle area are understandably disturbed. Who wouldn't be? Business firms are suffering; people are often harassed; and parents are worried about the safety and well-being of their children. But unfortunately one thing is as it has always been: No single sweeping solution is in sight - at least none that is free of crippling drawbacks. One recurring suggestion for curbing prostitution, for instance, is to have the police make more arrests. But no matter how many arrests are made, prostitutes are back on the streets in a matter of hours. Then how about more severe jail sentences for prostitutes? The courts have been unwilling to impose such penalties, especially in light of the overcrowding in the jails. And in any event police cannot be expected to devote endless resources to making arrests that have no effect on the situation.

Nevertheless, there are some imperfect but practical steps that can be taken at least to break up the sick and dangerous situation now prevailing around Thomas Circle. More severe fines should be imposed on the prostitutes and their customers. Police attention, at least temporarily, should be intense and wellnoted. This might help get the word aroound that the District is serious about curbing prostitution and related offenses. And it could - until the next time and the next place - scatter and weaken a squalid concentration of crime.