It may show to what degree one is worthy (6)
I believe the answer is:
thesis
'it may show to what degree' is the definition.
The definition suggests a singular noun which matches the answer.
'one is worthy' is the wordplay.
'one' becomes 'the' (both can introduce a definite example of something).
'is worthy' becomes 'sis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the'+'sis'='THESIS'
Can you help me to learn more?
(Other definitions for thesis that I've seen before include "Long dissertation written to obtain university degree" , "Dissertation - idea" , "theory" , "Researched dissertation" , "Dissertation presented for a doctorate" .)
