Plea from Somali bishop (5)
I believe the answer is:
alibi
'plea' is the definition.
(thesaurus)
'from somali bishop' is the wordplay.
'from' says the answer is hidden in the clue.
'ALIBI' is hidden in the letters of 'somali bishop'.
(Other definitions for alibi that I've seen before include "Defence that one was somewhere else at the time of a crime" , "A claim one was elsewhere when crime took place" , "Defence against accusation - was seen elsewhere at the time" , "Justification" , "Legal defence, plea" .)