After some green tea, pressure group attempted coup (9,4)
I believe the answer is:
gunpowder plot
'after some green' is the definition.
The definition suggests a singular noun which matches the answer.
'tea pressure group attempted coup' is the wordplay.
'tea' becomes 'gunpowder' (type of tea).
'pressure' becomes 'p' (scientific abbreviation).
'group attempted coup' becomes 'lot' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gunpowder'+'p'+'lot'='GUNPOWDER PLOT'
Can you help me to learn more?
(Other definitions for gunpowder plot that I've seen before include "Guy was actively involved in this" , "Thwarted conspiracy of 1605" , "Guy's planning" , "Sixteen zero five" , "Guy Fawkes's scheme" .)