Fungus (6)
'fungus' is the definition.
(I know that agaric is a type of fungus)
This is all the clue.
(Other definitions for agaric that I've seen before include "Fungus, eg, mushroom" , "Type of mushroom" , "fungal growth" , "Fungus of mushroom family" .)
'fungus' is the definition.
(type of plant comprised of a fungus and alga)
This is all the clue.
(Other definitions for lichen that I've seen before include "Symbiotic organism growing on a tree trunk or rock" , "Compound plant not unlike to moss in appearance" , "It grows on rocks and trees" , "Compound moss-like plant" , "Primitive plants found on rocks" .)
'fungus' is the definition.
(I know that mildew is a fungus)
This is the entire clue.
(Other definitions for mildew that I've seen before include "rot" , "Fungus that produces a white growth on organic matter" , "Fungal growth on plants" , "White coating on things exposed to damp" , "attack of disease" .)
(Another definition for dryrot that I've seen is " moral degeneration".)