Scoundrel keeping Oscar, behold in the shade (6)
I believe the answer is:
colour
'the shade' is the definition.
(I've seen this before)
'scoundrel keeping oscar behold' is the wordplay.
'scoundrel' becomes 'cur' (cur can mean a despicable person).
'keeping' is an insertion indicator.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'behold' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'o'+'lo'='olo'
'cur' enclosing 'olo' is 'COLOUR'.
'in' acts as a link.
(Other definitions for colour that I've seen before include "Blue or green, say" , "Quality that results from light reflection" , "black?" , "Hue, shade" , "'Tinge, hue (6)'" .)