The most common and most likely answer to this crossword clue is the 8 letter word CONGRESS
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More clues leading to the result CONGRESS
- US legislature apparently opposed to progress?
- House of sex
- Sex: Republicans have the edge here
- IT conference?
- 14 deception starts getting rumbled ever so slightly
- Legislature against initially granting remissions easily, says spokesman
- Caught wicked woman framing North American body
- French painter guillotined and entombed in island, for sexual act
- Assembly wanting advance? Con, not pro!
- Meeting some relations
Buddy explains!

The straight part
We know that "diet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case diet = congress.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CONGRESS mean?
CONGRESS noun- A coming together of two or more people; a meeting.
- A formal gathering or assembly; a conference held to discuss or decide on a specific question.
- (often capitalized: Congress) A legislative body of a state, originally the bicameral legislature of the United States of America.
- An association, especially one consisting of other associations or representatives of interest groups.
- Coitus; sexual intercourse.
- To assemble together.
- To meet in a congress.