A subterfuge no one's welcome to subvert (7)
I believe the answer is:
evasion
'a subterfuge' is the definition.
(I've seen this before)
'no one's welcome to subvert' is the wordplay.
I cannot really see how this works, but
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is found within the answer.
'one's' could be 'as' (a thing is one thing) and 'as' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for evasion that I've seen before include "Act of avoiding" , "Improper avoidance" , "prevaricating excuse" , "Subterfuge" , "Avoidance; equivocation" .)