Moving aft? That's rich! (3)
I believe the answer is:
fat
'rich' is the definition.
(rich can describe fat or creamy food)
'moving aft?' is the wordplay.
'moving' indicates anagramming the letters (letters are moved around).
'aft' with letters rearranged gives 'FAT'.
'that's' acts as a link.
(Other definitions for fat that I've seen before include "Corpulent; little (chance)" , "eg Lard" , "Portly" , "Substantial" , "Overweight, stout" .)