Balanced analysis may form, finally, a standard of measurement (9)
I believe the answer is:
symmetric
'balanced' is the definition.
(thesaurus)
'analysis may form finally a standard of measurement' is the wordplay.
'finally' says to take the final letters.
'a standard of measurement' becomes 'metric' (I've seen this before).
The last letters of 'analysis may form' are 'sym'.
'sym'+'metric'='SYMMETRIC'
(Other definitions for symmetric that I've seen before include "Regular" , "Equally balanced" .)