Source of wood, support for golfer crossing river (4)
I believe the answer is:
tree
'source' is the definition.
(I have seen 'Source of wood ' mean 'tree' so perhaps 'source' could also mean 'tree')
'wood support for golfer crossing river' is the wordplay.
I cannot really understand how this works, but
'river' could be 'r' (abbreviation for river) and 'r' is found in the answer.
'support' could be 'tee' (tee is a kind of support) and 'tee' is present in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for tree that I've seen before include "Oak, say" , "cross" , "Care for shoes" , "Theme" , "Plane possibly" .)