Distance when flying to check carbon disasters (9)
I believe the answer is:
accidents
'disasters' is the definition.
'distance when flying to check carbon' is the wordplay.
'when flying' indicates anagramming the letters (letters fly around).
'to check' means one lot of letters goes inside another (check can mean to restrain or block in).
'carbon' becomes 'c' (C is the chemical symbol for carbon).
'distance' with letters rearranged gives 'acidents'.
'acidents' enclosing 'c' is 'ACCIDENTS'.
(Other definitions for accidents that I've seen before include "mistakes" , "Unfortunate mishaps or chance events" , "Unforeseen mishaps" , "They do happen" .)