Sierra Leone's first professional stage actress is Tonie Tucker who will take the part of Sidi in The Lion and the Jewel by Wole Soyinka of Nigeria on the B.B.C. Third programme on Thursday. Tonie, who is 23, came to this country in 1962 with a government grant to study at the College of Dramatic Art in Glasgow. At the end of June she will play in a double bill presented at Hampstead Theatre Club by the Masques, a group formed this year who want to perform plays in London by African wrtiers. Their producer is Athol Fugard from South Africa. Their first plays, The Trials of Brother Jerome and The Strong Breed, are both by Wole Soyinka. ....