What the diplomat needs about one being silent (5)
I believe the answer is:
tacit
'being silent' is the definition.
('tacit' can be a synonym of 'silent')
'what the diplomat needs about one' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'about' could be 'c' (abbreviation for circa) and 'c' is present in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
The remaining letters 'at' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tacit that I've seen before include "Silently understood" , "Implied without being stated" , "Implied -- inferred" , "Wordless" , "Unspoken but understood" .)