Never-ending destiny to be overweight (3)
I believe the answer is:
fat
'be overweight' is the definition.
(similar in meaning)
'never-ending destiny' is the wordplay.
'never ending' means to remove the last letter.
'destiny' becomes 'fate' (synonyms).
'fate' with its last letter taken away is 'FAT'.
'to' acts as a link.
(Other definitions for fat that I've seen before include "Obese, overweight" , "Greasy substance" , "Adipose tissue" , "Like 10 ac" , "eg Lard" .)