Stressed from being off centre? Au contraire! (2,4)
I believe the answer is:
on edge
'stressed' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for on edge that I've seen before include "All agog" , "close to border" , "Tense and irritable, very nervous" , "Twitchy" , "Cliff-top walker may be" .)