He eats it messily in dither (8)
I believe the answer is:
hesitate
'dither' is the definition.
(I've seen this before)
'he eats it messily' is the wordplay.
'messily' indicates an anagram.
'eats'+'it'='eatsit'
'eatsit' with letters rearranged gives 'sitate'.
'he'+'sitate'='HESITATE'
'in' is the link.
(Other definitions for hesitate that I've seen before include "Dither indecisively" , "Vacillate" , "Falter, delay" , "Pause, think twice" , "Do this perhaps to be lost" .)