Heavy rain accompanied by lightning? (5,5)
I believe the answer is:
flash flood
'heavy rain' is the definition.
The definition and answer can be both types of natural phenomena as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'accompanied by lightning?' is the wordplay.
'accompanied' becomes 'flood' (I can't explain this - if you can you should believe this answer much more).
'by' is a charade indicator (letters next to each other).
'lightning?' becomes 'flash' (lightning is a kind of flash).
'flood' after 'flash' is 'FLASH FLOOD'.
Can you help me to learn more?
(Another definition for flash flood that I've seen is " Sudden deluge".)