Mystery unravelled around end of film giving a sense of harmony and balance (8)
I believe the answer is:
symmetry
'a sense of harmony and balance' is the definition.
'mystery unravelled around end of film' is the wordplay.
'unravelled' is an anagram indicator.
'around' is an insertion indicator.
'end of' says to take the final letters.
The last letter of 'film' is 'm'.
'mystery' anagrammed gives 'symetry'.
'symetry' placed around 'm' is 'SYMMETRY'.
'giving' acts as a link.
(Other definitions for symmetry that I've seen before include "Balance in appearance" , "Due proportion" , "Exact correspondence between parts" , "Balance between two parts" , "Regularity of shape" .)