These prophets could be so clear (7)
I believe the answer is:
oracles
'these prophets' is the definition.
('oracle' can be a synonym of 'prophet')
'could be so clear' is the wordplay.
'could be' indicates anagramming the letters.
'so'+'clear'='soclear'
'soclear' with letters rearranged gives 'ORACLES'.
(Other definitions for oracles that I've seen before include "Wise utterances" , "Authoritative sources" , "Authoritative statements" , "Solacer for wise or knowledgeable people" , "Prophets, seers" .)