Sunday Post

[bobmaim]

Stuck on four,12a A national source for sand,essentially -e---n.
16a Sweet left in cooler ----
13d Got by elderly chap in front ----g-l
17d she's left with distinctive character --u-o

[boxtops]

bob - how many letters in each answer?

It's really hard to count dashes this end, better if you use ?? for missing letters.

[Lie-in King]

12a German (a national) - 'germ' (source) + (s)an(d)
16a F-L-an

17d L-aura

[Calibax]

17d L aura if your O is wrong

[Valanne]

13d managed

[Lie-in King]

13d Man-aged (?)

[Calibax]

13d Man aged

[bobmaim]

Thanks everyone for your help