Supports reverting to stocking sources of wood (9)

'sources of wood' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Maybe there's an association between them I don't understand?

'supports reverting to stocking' is the wordplay.
'supports' becomes 'forests' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'reverting' is a reversal indicator.
'stocking' means one lot of letters goes inside another ('stock' can mean 'fill').
'to' in reverse letter order is 'ot'.
'forests' enclosing 'ot' is 'FOOTRESTS'.

Can you help me to learn more?