Use trickery, though against it (3)
I believe the answer is:
con
'use trickery' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'against it' is the wordplay.
I cannot really see how this works, but
'against' could be 'on' (on can mean by or up against) and 'on' is located in the answer.
A single letter 'c' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'though' is the link.
Can you help me to learn more?
(Other definitions for con that I've seen before include "Not in favour" , "one in pen?" , "Deceive; disadvantage" , "Tory" , "Informally swindle" .)