Shocked as fat on bread gets spread (13)
I believe the answer is:
flabbergasted
'shocked' is the definition.
(I've seen this in another clue)
'fat on bread gets spread' is the wordplay.
'fat' becomes 'flab' (flab is a kind of fat).
'on' says to put letters next to each other.
'spread' is an anagram indicator.
'bread'+'gets'='breadgets'
'breadgets' anagrammed gives 'bergasted'.
'flab'+'bergasted'='FLABBERGASTED'
'as' acts as a link.
(Other definitions for flabbergasted that I've seen before include "Thunderstruck" , "Gobsmacked" , "Greatly surprised" , "Astonished" , "Dumbfounded" .)