Aircraft, extremely heavy, to fall by road (10)
I believe the answer is:
hydroplane
'aircraft' is the definition.
(hydroplane is a kind of aircraft)
'extremely heavy to fall by road' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'to' says to put letters next to each other.
'fall by' becomes 'drop' (synonyms. I am not sure about the 'by' bit.).
'road' becomes 'lane' (a lane is a small road).
'heavy' with its centre removed is 'hy'.
'hy'+'drop'+'lane'='HYDROPLANE'
Can you help me to learn more?
(Other definitions for hydroplane that I've seen before include "Skim across water at high speed" , "Boat that lifts out of the water at high speeds" , "Motorboat with foils" , "Speedboat" .)