Diagram showing a good way to play the harp? (5)
I believe the answer is:
graph
'diagram' is the definition.
(graphing is a kind of diagraming)
'a good way to play the harp?' is the wordplay.
'a good way' becomes 'g' (I can't justify this - if you can you should give a lot more credence to this answer).
'to play' indicates an anagram.
'harp' anagrammed gives 'raph'.
'g'+'raph'='GRAPH'
'showing' is the link.
Can you help me to learn more?
(Other definitions for graph that I've seen before include "Diagram representing relationships between quantities" , "Visual representation" , "Diagram showing the relationship between variable quantities" , "Plotted diagram" , "Diagram showing relationships between things" .)