A letter must be changed in each clue before solving. There is also 1 clash...
2a Delia's vessel, perhaps, floated past sheltering snake (9,2 words) S??M? / BOAT The correct letter is T i think...
3d A sound character, retired Penny, made up for kissing things (4) ??T? possibly Missing?
sorry been away from pc and only just looked in....yes that T was in the wrong place ... i worked out that the clash was in the cell 9a/3d met ...and that 2 numbers were involved...
I used the arabic numeral - X could be ambiguous (sorry about the confusion over the typo - Neveracrossword guessed right).
The number following the double letter cell tells you which one to choose - if you know the scale (or check wiki).
I'd have left it but for hankir's following question, Neveracrossword - he couldn't have known what saladdodger had in there (it did get a bit wordy, though!).