Show a tree by a river (6)
I believe the answer is:
oliver
'show a' is the definition.
I can't judge whether this definition defines the answer.
'tree by a river' is the wordplay.
I cannot quite understand how this works, but
'tree' could be 'olive' (olive is a kind of tree) and 'olive' is found in the answer.
'river' could be 'r' (abbreviation for river) and 'r' is present in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for oliver that I've seen before include "Dickensian musical" , "Master Twist" , "Cromwell, for example" , "- Goldsmith (She Stoops to Conquer)" , "Dickens boy who asked for more, and a musical comedy" .)