Where there's many a cut in timber supplies (7)
I believe the answer is:
sawmill
'where there's many a' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'cut in timber supplies' is the wordplay.
'cut' becomes 'saw' (sawing is a kind of cutting).
'in timber supplies' becomes 'mill' (I can't explain this - if you can you should believe this answer much more).
'saw'+'mill'='SAWMILL'
Can you help me to learn more?
(Other definitions for sawmill that I've seen before include "workplace that can produce deal" , "Log cutting plant" , "Place where timber is cut into planks" , "Timber works" , "Cutting workplace" .)