Simple decision that’s up for review (15)
I believe the answer is:
unsophisticated
'simple' is the definition.
(I've seen this before)
'decision that's up for review' is the wordplay.
'for review' is an anagram indicator.
'decision'+'thats'+'up'='decisionthatsup'
'decisionthatsup' is an anagram of 'UNSOPHISTICATED'.
(Other definitions for unsophisticated that I've seen before include "straightforward" , "Simple" , "green" , "Lacking experience" , "crude" .)