Slander (mere speech, not broadcast or written ) is,normally only actionable on proof of actual loss, not merely loss of reputation. A quaint exception at common law is where a woman's chastity or morality has been impugned.
As stated ,legal aid is not available for it, nor for libel .Libel is defamation recorded in some 'permanent' form (printed etc) or broadcast.
The law is that way because the courts would be overloaded if everyone could sue every time they were the victim of some gossipy person. Some of us would be in court every day, otherwise ! It also reflects common sense, because people are presumed to take such oral statements with a pinch of salt. The law takes a more serious view of libel, judging that anything written is more lasting,likely to be more widely disseminated and far more likely to be taken as having truth to it.
Best course is to trust to the common sense of any hearer and to rest on your true reputation.