Spy from the East meets Greek character and Bond's boss -- shh! (4,3)

'spy from the east' is the definition.
The definition and answer can be both to do with communicating as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?

'meets greek character and bond's boss shh' is the wordplay.
'meets' means one lot of letters go next to another.
'greek character' becomes 'mu' (letter from the Greek alphabet).
'and' is a charade indicator (letters next to each other).
'bond's boss' becomes 'm' (M is the head of MI6 in the James Bond series).
'shh' becomes 'keep' (I can't explain this - if you can you should give a lot more credence to this answer).
'mu'+'m'='mum'
'mum' put after 'keep' is 'KEEP MUM'.

Can you help me to learn more?