Do they tell the dairy farmer bad weather is approaching? (4)
I believe the answer is:
lows
'do they tell the dairy farmer bad' is the definition.
The definition suggests an adverb but the answer is not.
'weather is approaching?' is the wordplay.
'weather' becomes 'low' (low is a kind of weather).
'is approaching?' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'low'+'s'='LOWS'
Can you help me to learn more?
(Other definitions for lows that I've seen before include "Cyclones" , "Depressions" , "Minimum levels" , "Moos" .)