Cryptic crossword No 3,517

Across

1. When he's a bit bigger, he'll come out of his shell (6,4)
2. Doctor claimed to be involved in treatment (7)
3. Be aware of large limits to understanding (9)
4. Mad scientist is matter-of-fact and incredibly intense (12)
5. Main office splits into four sectors after boss' arrival (12)
6. Latticework conceals roof space (5)
7. Took the mickey out of a school activity then died (4)
8. Rough fabric, one of those that came over from Denmark (4)
9. City on Missouri apparently had administrators put their heads together (5)
10. A matter of life and death for tame viper I disturbed (10)
11. To this overture I have added five notes initially producing desired result (9)
12. Not entirely off if teenager's two years older than Juliet (7)
13. The French originally Italian-born novelist inspired zealous German philosopher (7)
14. Hopelessness of the French couple (7)

Down

1. Articulated control in period in power (5)
2. Grabbed sixteen for the French deputy head (6)
3. University town roughly where The Archers is set (9)
4. 2240 pounds given to Andrew Mountbatten-Windsor once in university town (9)
5. Expert in martial arts starts to jump up and down... Acceptable answer! (6)
6. Her award for refurbishing monitors, keyboards, printers and so on (8)
7. Intertwine clean components with bed stuffing (6)
8. Marsh holds everyone killed in battle (6)
9. Scrub some of this courtyard (5)
10. Plan time to get 26 reorganised (6)
11. Recklessly high temperatures overwhelm 500 coniferous trees (9)
12. Camilla gets stuck into risque entertainment (5)
13. A pair of Charlies seizing mixed media lecturer (8)
14. Team up with reportedly a young female horse, not quite nine (9)
15. Egghead gets involved in return of staunch encounters (5)
16. Creamy dessert served up with a hot fibrous vegetable (6)