Way a prisoner is in prison (6)
I believe the answer is:
stalag
'in prison' is the definition.
The definition suggests a singular noun which matches the answer.
'way a prisoner' is the wordplay.
'way' becomes 'st' (abbreviation for street).
'prisoner' becomes 'lag' (slang term).
'st'+'a'+'lag'='STALAG'
'is' is the link.
Can you help me to learn more?
(Other definitions for stalag that I've seen before include "WWII German prisoner of war camp" , "Water at the mouth" , "German camp for POWs" , "German prison camp in WW2" , "German World War two prison camp" .)