"Doubt" set in quotes (8)
I believe the answer is:
question
'doubt' is the definition.
(I know that doubt can be written as question)
'set in quotes' is the wordplay.
'set' is an anagram indicator (instruction to set the letters).
'in'+'quotes'='inquotes'
'inquotes' is an anagram of 'QUESTION'.
(Other definitions for question that I've seen before include "Challenge" , "Ask; doubt" , "What could initiate this" , "dispute" , "Query" .)