Plunged Heads of Department into poverty preceding economic downturn (6)
I believe the answer is:
dipped
'plunged' is the definition.
(dipping is a kind of plunging)
'heads of department into poverty preceding economic downturn' is the wordplay.
'heads of' indicates taking the first letters.
The initial letters of 'department into poverty preceding economic downturn' is 'DIPPED'.
(Other definitions for dipped that I've seen before include "Briefly submerged" , "Like lowered headlights" , "Immersed momentarily" , "Lowered into liquid" , "Lower beam of headlights" .)