A measure employed by the chap in the dock (7)
I believe the answer is:
accused
'the chap in the dock' is the definition.
I can't tell whether this defines the answer.
'a measure employed' is the wordplay.
'measure' becomes 'cc' (cc is a kind of measure).
'employed' becomes 'used' ('use' can be a synonym of 'employ').
'a'+'cc'+'used'='ACCUSED'
'by' is the link.
Can you help me to learn more?
(Other definitions for accused that I've seen before include "Indicted" , "Charged with an offence" , "Defendant in a criminal proceeding" , "Blamed" , "Person being charged" .)