Sound reason for corvine cries (4)
I believe the answer is:
caws
'corvine cries' is the definition.
(I know this)
'sound reason' is the wordplay.
'sound' indicates a 'sounds like' (homophone) clue.
'reason' becomes 'cause' (I've seen this in another clue).
'cause' is a homophone of 'CAWS'.
'for' is the link.
(Other definitions for caws that I've seen before include "Cries of murder" , "Harsh cries of crows" , "Rook calls" .)