Barely discernible number between 500 and 1000 (3)
I believe the answer is:
dim
'barely discernible' is the definition.
I can't judge whether this defines the answer.
'number between 500 and 1000' is the wordplay.
'number' becomes 'i' (I is an example).
'between' indicates putting letters inside.
'500' becomes 'D' (Roman numeral for 500).
'and' is a charade indicator (letters next to each other).
'i000' becomes 'M' (roman numeral).
'd'+'m'='dm'
'i' put within 'dm' is 'DIM'.
Can you help me to learn more?
(Other definitions for dim that I've seen before include "Unintelligent; badly lit" , "Darken" , "Opaque, not bright" , "Not bright or distinct" , "Unpromising" .)