Futile to economise (7)
I believe the answer is:
useless
'futile' is the definition.
(similar in meaning)
I don't understand how the rest of the clue works.
(Other definitions for useless that I've seen before include "Not worth a jot" , "Serving no practical purpose" , "Without any worthwhile application" , "Of no practical application, not worth keeping" , "Fruitless" .)