Here we go - I've now completed the crossword but need some explanations, please.
12 across 'One vegetable out of 10', answer Pea (because it fits into the space) - don't know where this comes from
5 down 'Scarce -and in demand (Gotcha?)', answer 'At a premium'. Apart from 'at' I haven't a clue how we get the rest of the answer