Stout wife initially accepting Muslim decree (5)
I believe the answer is:
fatwa
'muslim decree' is the definition.
(a fatwa is an Islamic legal ruling)
'stout wife initially accepting' is the wordplay.
'stout' becomes 'fat' (similar in meaning).
'wife' becomes 'w' (abbreviation).
'initially' suggests taking the first letters.
The initial letter of 'accepting' is 'a'.
'fat'+'w'+'a'='FATWA'
(Other definitions for fatwa that I've seen before include "Islamic decree" , "Muslim ruling" , "Ruling or sentence by Islamic religious leader" , "Ruling by Islamic leader, as on Salmon Rushdie" , "Islamic sentence as on Salman Rushdie" .)