She's anything but worthless! (4)
I believe the answer is:
ruby
'she's' is the definition.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ruby that I've seen before include "Gemstone comprising mainly aluminium oxide" , "Vivid red" , "Jack perhaps" , "Deep 6 across" , "A red jewel" .)