Detect only a small amount (5)
I believe the answer is:
trace
This might be a double definition.
'detect only' is the first definition.
'trace' can be an answer for 'detect' (I've seen this before). I'm not certain of the 'only' bit.
'a small amount' is the second definition.
(I've seen this in another clue)
Can you help me to learn more?
(Other definitions for trace that I've seen before include "Evidence" , "Copy by drawing on translucent paper" , "Locate by investigation" , "Scarcely detectable amount" , "Discover - modicum" .)