Second-guess public relations decree (7)
I believe the answer is:
predict
'second-guess' is the definition.
(second-guess can mean to attempt to predict)
'public relations decree' is the wordplay.
'public relations' becomes 'PR' (abbreviation).
'decree' becomes 'edict' (synonyms).
'pr'+'edict'='PREDICT'
(Other definitions for predict that I've seen before include "Foretell, prophesy" , "Forecast" , "Anticipate" , "act as oracle" , "Foresee" .)