Is he in prison for the century ahead? (3)
I believe the answer is:
con
'is he in prison for' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'century ahead?' is the wordplay.
'century' becomes 'C' (common abbreviation).
'ahead?' becomes 'on' ('on' can be a synonym of 'ahead').
'c'+'on'='CON'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for con that I've seen before include "Direct steering; study" , "Rook" , "politician who's in the right" , "Swindle after winning trust" , "Swindle; steer" .)