Discover a barely discernible amount (5)
I believe the answer is:
trace
This clue is a double definition.
'discover' is the first definition.
(thesaurus)
'a barely discernible amount' is the second definition.
(I've seen this in another clue)
(Other definitions for trace that I've seen before include "Element" , "Skimpy garment" , "Detect - track" , "Track; small quantity" , "Copy; describe; draw" .)