Large numbers in the US suddenly turn on south (5)
I believe the answer is:
slews
'large numbers' is the definition.
(I've seen this in another clue)
'suddenly turn on south' is the wordplay.
'suddenly turn' becomes 'slew' (I've seen this before).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'south' becomes 's' (abbreviation).
'slew'+'s'='SLEWS'
'in the us' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for slews that I've seen before include "lurches violently" , "Skids, bringing a vehicle's back-end around" .)