More widespread tree over well… (5)
I believe the answer is:
rifer
'more widespread' is the definition.
(I've seen this in another clue)
'tree over well' is the wordplay.
'tree' becomes 'fir' (fir tree is a kind of tree).
'over' is a reversal indicator.
'well' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'fir' back-to-front is 'rif'.
'rif'+'er'='RIFER'
Can you help me to learn more?
(Other definitions for rifer that I've seen before include "Commoner" , "More abundant" .)