Senior officials, one tight-lipped about April 1 birthday? (11)

'senior officials' is the definition.
The definition and answer can be both people as well as being plural nouns.
Maybe you can see an association between them that I don't see?

'one tight-lipped about april 1 birthday?' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'about' could be 're' ('re' means regarding or about) and 're' is found within the answer.
'1' could be 'a' (both can mean one) and 'a' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?