What remains of one's equilibrium (7)
I believe the answer is:
balance
'equilibrium' is the definition.
(balance is a kind of equilibrium)
'what remains of one's' is the wordplay.
I cannot quite see how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for balance that I've seen before include "Rest" , "emotional stability" , "Libra - amount in account" , "Sign" , "Weighing device" .)