Understood diplomacy in concealing one (5)
I believe the answer is:
tacit
'understood' is the definition.
(I've seen this before)
'diplomacy in concealing one' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'diplomacy' could be 'tact' (tact can mean diplomacy or sensitivity) and 'tact' is located in the remaining letters.
No letters remain.
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 "Implied without being put into words" , "Understood, not spoken or played" , "Implicit, unspoken" , "Not said though understood" , "Attic? (anag)" .)