Hello jennifer,
sorry but just found this thread and you seem very knowledgeable and helpful!  I am struggling with the last four of this very good puzzle! 
Any help with numbers 10, 20, 21 & 97 would be very gratefully received
10 - Nothing clear, unfortunately enveloped in gas in the boats (8) 
20 - Put your foot in it - a query surrounds the vessel (6 )
21 - Doctor, enthralled by destiny, had time to become a high-flyer ( 7, 4) 
97 - Well-organised charmer all in tune around most of the oceans ( 5, 9 ) 
Can try and reciprocate with some other answers if necessary!