Sample the ability to discern what is of good quality (5)
I believe the answer is:
taste
'sample' is the definition.
(I know that sample can be written as taste)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for taste that I've seen before include "Predilection" , "Decorum" , "Discrimination - a sense" , "Perceive the flavour" , "Small portion" .)