not doing too well here.
15A - A sound signified they say, that of Linton's Dundas (9) I have ??O?????T
19A - Ibsen character richest in adversity (9) I have ??R?????? - christien ?
3D - cornered, it's marginal (8,4) I have S?O?L???N?T? - something note ?
11D - strange siblings may change sides with writers (5,7) I have ?E?R???S????