Keep quiet about free latte's secret state (7)
I believe the answer is:
stealth
'secret state' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'keep quiet about free latte's' is the wordplay.
'keep quiet' becomes 'sh' (as in shushing someone).
'about' means one lot of letters goes inside another.
'free' indicates an anagram.
'latte' with letters rearranged gives 'tealt'.
'sh' enclosing 'tealt' is 'STEALTH'.
Can you help me to learn more?
(Other definitions for stealth that I've seen before include "Quiet or secret way of behaviour" , "Cautious and surreptitious action or movement" , "Cats display this" , "By which taxes go up" , "Unseen machination" .)