This ones not making sense. I'm sure of all connecting letters and other clues are correct.
6d. Down-at-heel area of Italy (7) S _ L _ N _ O
and yes I've considered SALERNO but the N above is correct because 12a refers to E Africa's largest solitary volcanic mountain's gone erupting around lake. (Mount Elgon is the volcanic mountain & GONE erupting around Lake makes anagram of GONEL).