Holding container, present greenstuff (7)
I believe the answer is:
herbage
'greenstuff' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'holding container present' is the wordplay.
'holding' is an insertion indicator.
'container' becomes 'bag' (bag is a kind of container).
'present' becomes 'here' (both can mean in attendance).
'bag' going inside 'here' is 'HERBAGE'.
Can you help me to learn more?
(Other definitions for herbage that I've seen before include "Plant life" , "Vegetation" .)