Picked up plant expected to produce fungus (6)
I believe the answer is:
mildew
'fungus' is the definition.
(I know that mildew is an fungus)
I cannot understand how the remainder of the clue works.
(Other definitions for mildew that I've seen before include "White coating on things exposed to damp" , "Fungal disease in plants" , "Fungal plant disease" , "rot" , "White powdery fungus" .)