Convoluted mystery involving maiden's pleasing form (8)
I believe the answer is:
symmetry
'pleasing form' is the definition.
(symmetry is visually pleasing)
'convoluted mystery involving maiden's' is the wordplay.
'convoluted' is an anagram indicator.
'involving' indicates putting letters inside.
'maiden' becomes 'm' (cricket abbreviation).
'mystery' with letters rearranged gives 'symetry'.
'symetry' going around 'm' is 'SYMMETRY'.
(Other definitions for symmetry that I've seen before include "Due proportion" , "Proportion; beauty of form" , "Arrangement of parts in pleasing proportions" , "Property of this grid" , "Exact correspondence between parts" .)