The most common and most likely answer to this crossword clue is the 4 letter word BANS
B
A
N
S
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The straight part
We know that "Forbids" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case forbids = bans.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 BANS mean?
BANS noun- Prohibition.
- A public proclamation or edict; a summons by public proclamation. Chiefly, in early use, a summons to arms.
- The gathering of the (French) king's vassals for war; the whole body of vassals so assembled, or liable to be summoned; originally, the same as arrière-ban: in the 16th c., French usage created a distinction between ban and arrière-ban, for which see the latter word.
- A curse or anathema.
- A pecuniary mulct or penalty laid upon a delinquent for offending against a ban, such as a mulct paid to a bishop by one guilty of sacrilege or other crimes.
- To summon; to call out.
- To anathematize; to pronounce an ecclesiastical curse upon; to place under a ban.
- To curse; to execrate.
- To prohibit; to interdict; to proscribe; to forbid or block from participation.
- To curse; to utter curses or maledictions.
- A unit measuring information or entropy based on base-ten logarithms, rather than the base-two logarithms that define the bit.
- A title used in several states in central and south-eastern Europe between the 7th century and the 20th century.