A man of conviction (3)
I believe the answer is:
lag
This clue could be a double definition.
'a man' is the first definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'conviction' is the second definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'of' acts as a link.
Can you help me to learn more?
(Other definitions for lag that I've seen before include "Convict (slang)" , "Old convict - dally - insulate" , "Get behind; convict" , "Insulate (pipes)" , "Fall behind with gal" .)