One man for Caesar to beware of (4)

I believe the answer is:

ides

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'caesar to beware of' is the definition.
I can't judge whether this defines the answer.

'one man' is the wordplay.
'one' becomes 'I' (Roman numeral).
'man' becomes 'des' ().
'i'+'des'='IDES'

'for' is the link.

Can you help me to learn more?

(Other definitions for ides that I've seen before include "Caesar was killed in this side of March" , "Caesar's fateful day" , "15/7?" , "Julius Caesar died in these March days" , "mid-month for the Romans" .)

I've seen this clue in the Evening Standard.

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