Solved mystery about opening of minister correspondence (8)
I believe the answer is:
symmetry
'correspondence' is the definition.
(synonyms)
'solved mystery about opening of minister' is the wordplay.
'solved' indicates an anagram (the anagram must be solved).
'about' indicates putting letters inside.
'opening of' suggests taking the first letters.
The first letter of 'minister' is 'm'.
'mystery' anagrammed gives 'symetry'.
'symetry' enclosing 'm' is 'SYMMETRY'.
(Other definitions for symmetry that I've seen before include "Balance in appearance" , "Proportion; beauty of form" , "Due proportion" , "Exact correspondence between parts" , "Pleasing proportion between parts of a whole" .)