All the same, they're overwhelmed by its fine quality (5)
I believe the answer is:
equal
'all the same' is the definition.
(I've seen this in another clue)
'overwhelmed by its fine quality' is the wordplay.
'overwhelmed by' indicates the answer is hidden within the clue (the clue has absorbed or overwhelmed the answer).
'EQUAL' is hidden within 'its fine quality'.
'they're' acts as a link.
(Other definitions for equal that I've seen before include "Uniform" , "The same; fairly balanced" , "Level" , "The same in quantity, status etc" , "Evenly matched" .)