Unintelligible (10)
(Other definitions for garbled that I've seen before include "(Message) corrupted" , "Mixed-up" , "Confused, disjointed" , "Disjointed, incoherent" , "Unintentionally jumbled" .)
'unintelligible' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for incoherent that I've seen before include "Confused" , "rambling" , "Internally inconsistent" , "drunk?" , "difficult to understand" .)