Mend one end of the shelf, I figure (3)
I believe the answer is:
fix
'mend' is the definition.
(synonyms)
'one end of the shelf i figure' is the wordplay.
'one end of the' says to take the final letters.
'i figure' becomes 'ix' (I am not sure about this - if you are sure you should believe this answer much more).
The final letter of 'shelf' is 'f'.
'f'+'ix'='FIX'
Can you help me to learn more?
(Other definitions for fix that I've seen before include "Arrange" , "Sort out" , "mess" , "Fasten" , "Mend" .)