Heavy weather made of first day at work before long (7)
I believe the answer is:
monsoon
'heavy weather' is the definition.
(I've seen this in another clue)
'first day at work before long' is the wordplay.
'first day' becomes 'm' (I can't justify this - if you can you should give a lot more credence to this answer).
'at work' becomes 'on' (on can mean activated or working).
'before long' becomes 'soon' (synonyms).
'm'+'on'+'soon'='MONSOON'
'made of' acts as a link.
Can you help me to learn more?
(Other definitions for monsoon that I've seen before include "Seasonal wind or rainy season in S Asia" , "Wet seasonal wind" , "Seasonal Indian Ocean wind" , "Rainy season of India and SE Asia" , "Season of heavy rain" .)