Struck one forcibly such food is fattening (8)
I believe the answer is:
battered
'struck' is the definition.
(battering is a kind of striking)
'one forcibly such food is fattening' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'er' (I've seen this in other clues) and 'er' is present in the answer.
'food' could be 'e' (E is an example) and 'e' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for battered that I've seen before include "Ill-treated (as cod might be?)" , "Injured; like fried fish" , "Beaten-up, knocked about" , "Struck violently and repeatedly" , "Beaten" .)