Crisis with English vehicle missing a crossing over French sea (9)
I believe the answer is:
emergency
'crisis' is the definition.
(I know that emergency is a type of crisis)
'crossing over french sea' is the wordplay.
'crossing' becomes 'egency' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'over' indicates putting letters inside.
'french sea' becomes 'mer' ('sea' in French).
'egency' going around 'mer' is 'EMERGENCY'.
'with english vehicle missing a' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for emergency that I've seen before include "Serious situation needing prompt action" , "Serious situation requiring immediate action" , "Occurrence demanding immediate remedy" , "Serious casualty" , "Sudden occurrence necessitating urgent action" .)