Varying in quality, like a much-mended garment (6)
I believe the answer is:
patchy
'varying' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I can't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for patchy that I've seen before include "Uneven in quality like repaired clothes" , "Often repaired" , "Morose" , "Uneven in quality - mended too often" , "Uneven in quality; showing signs of repair" .)