Scottish child's character black knight protects (5)
I believe the answer is:
bairn
'scottish child's' is the definition.
(I've seen this before)
'character black knight protects' is the wordplay.
'character' becomes 'air' (air can mean a character or mood).
'black' becomes 'b' (as in pencil classifications).
'knight' becomes 'n' (chess abbreviation).
'protects' indicates putting letters inside (outer letters protect inside letters).
'b'+'n'='bn'
'air' placed into 'bn' is 'BAIRN'.
(Other definitions for bairn that I've seen before include "little one in Yorkshire" , "Wee child" , "Northern child" , "Scot. child" , "A tot of Scotch" .)