Cryptic crossword No 3,938

Across

1. Danger cultivated in plot (6)
2. Breathing aids from airlines flying, when iodine is replaced by hydrogen (8)
3. Release unsafe criminal, initially needing time (8)
4. Provoke requirement with the French (6)
5. Applauding criminal initially overtaking on the track (8)
6. Still a train toys around (10)
7. Work out shape (6)
8. Positive outlook found in “Stop Tim — is madness!” (8)
9. Gloomy character at extremes of existence long ago (6)
10. Observe university, reportedly, afterwards—goodbye! (3,3,5)
11. Time belonging to us, we hear (4)
12. Instance of legal proceedings (4)
13. English vans beside French town in Indiana (10)

Down

1. King will aim recklessly (7)
2. Something extra to complete the newspaper? (10)
3. Oil plant regarding Sunday best (8)
4. Cheers — a long tour isn’t arranged with California (15)
5. Pressure to emphasise (6)
6. Award initially excites many more youngsters (4)
7. Generally, like a measuring instrument cut short (2,1,4)
8. Frozen formations found when the police shelve suspicions (3,7)
9. Whatever comes from any night out (8)
10. Filters melodies and injuries (7)
11. Childish Latin lad on French island (7)
12. Elaborate gold for Nathaniel, briefly (6)
13. Unable to hear fade out (4)