A major wind system with a way of working north before long (7)
I believe the answer is:
monsoon
'a major wind system' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'with a way of working north before long' is the wordplay.
'with' says to put letters next to each other.
'a way of working' becomes 'mo' (abbreviation for modus operandi).
'north' becomes 'N' (abbreviation).
'before long' becomes 'soon' (synonyms).
'mo'+'n' is 'mon'.
'mon'+'soon'='MONSOON'
Can you help me to learn more?
(Other definitions for monsoon that I've seen before include "Seasonal wind and rain in S Asia" , "Seasonal Asian wind" , "Rain-bringing wind" , "Wet seasonal wind" , "Asian wind; rainy season" .)