Unavailing suggestion for economy (7)
I believe the answer is:
useless
'unavailing' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for useless that I've seen before include "Ineffective" , "Not worth a jot" , "Without purpose" , "Lacking in purpose" , "Good-for-nothing" .)