Man would develop ultimate in quince jams, a key part of sustainable farming (8)
I believe the answer is:
hedgerow
'man' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'would develop ultimate in quince jams a key part of sustainable farming' is the wordplay.
I cannot really see how this works, but
'would' could be 'd' (as in 'we'd' - 'we would') and 'd' is present in the answer.
'key' could be 'g' (musical key) and 'g' is found in the answer.
'part' could be 'row' (row is a kind of part) and 'row' is located in the answer.
The remaining letters 'hee' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hedgerow that I've seen before include "Growth around field" , "Greenery between fields" , "Living boundary between fields" , "Field boundary" , "Field border" .)