Complete mess, it's said (5)
I believe the answer is:
whole
'complete' is the definition.
(similar in meaning)
'mess it's said' is the wordplay.
'mess' becomes 'hole' (synonyms).
'it's said' indicates a 'sounds like' (homophone) clue.
'hole' is a homophone of 'WHOLE'.
(Other definitions for whole that I've seen before include "undamaged" , "All the components" , "Integral" , "In entirety" , "Entire, undivided" .)