Rewrite other conclusion to unsatisfactory hypothesis (6)
I believe the answer is:
theory
'hypothesis' is the definition.
(I know that hypothesis can be written as theory)
'rewrite other conclusion to unsatisfactory' is the wordplay.
'rewrite' indicates anagramming the letters.
'conclusion to' indicates one should take the final letters.
The final letter of 'unsatisfactory' is 'y'.
'other' anagrammed gives 'theor'.
'theor'+'y'='THEORY'
(Other definitions for theory that I've seen before include "Hypothesis - doctrine" , "Set of ideas formed from reasoning" , "Proposition, thesis" , "The words, as opposed to the practice" , "Set of principles on which practice is based" .)