Cope, breaking one’s high standards (6)
I believe the answer is:
ideals
'high standards' is the definition.
(I've seen this before)
'cope breaking one's' is the wordplay.
'cope' becomes 'deal' ('deal' can be a synonym of 'cope').
'breaking' means one lot of letters goes inside another.
'one's' becomes 'is' (roman numeral).
'deal' inserted inside 'is' is 'IDEALS'.
(Other definitions for ideals that I've seen before include "100%? > 10 out out of 10? > With capital, more would want these" , "They're perfect" , "Dreams" , "Standards to be aimed at" , "Models of excellance" .)