Air for which wealth can be obtained (4)
I believe the answer is:
tune
'air' is the definition.
(air can mean a piece of music)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tune that I've seen before include "Adjust for better performance" , "Adjust (car engine); air" , "strain" , "Improve quality" , "Optimise the condition of" .)