Washington agency to go into declaration (5,10)
I believe the answer is:
state department
'washington agency to go into declaration' is the definition.
I can't judge whether this definition defines the answer.
'washington agency to go into declaration' is the wordplay.
'washington agency' becomes 'depart' (I can't explain this - if you can you should give a lot more credence to this answer).
'to go into' indicates putting letters inside (some letters go into others).
'declaration' becomes 'statement' (I've seen this before).
'depart' put inside 'statement' is 'STATE DEPARTMENT'.
Can you help me to learn more?
(Other definitions for state department that I've seen before include "Washington office" , "US Foreign Office" , "American diplomats" , "US officials" , "government agency abroad" .)