One making landfall? (9)
I believe the answer is:
avalanche
'landfall?' is the definition.
(I've seen this before)
'one' is the wordplay.
I cannot quite see how this works, but
'one' could be 'an' (I've seen this in other clues) and 'an' is located in the answer.
This may be the basis of clue (or it may be nonsense).
'making' acts as a link.
(Other definitions for avalanche that I've seen before include "Sudden descent of massed snow etc" , "sudden rush" , "Snow slip" , "serious fall" , "Snowslip" .)