Sad after rising workers' organisation fell (3,4)
I believe the answer is:
cut down
'fell' is the definition.
(I've seen this before)
'sad after rising workers' organisation' is the wordplay.
'sad' becomes 'down' (I've seen this before).
'after' says to put letters next to each other.
'rising workers' organisation' becomes 'cut' (I am not sure about this - if you are sure you should believe this answer much more).
'down' put after 'cut' is 'CUT DOWN'.
Can you help me to learn more?
(Other definitions for cut down that I've seen before include "Economise or despatch with sword" , "Reduce the length of" , "Felled" , "Fell a tree or reduce usage as in a diet" .)