Spies with initially obtuse greeting (4)
I believe the answer is:
ciao
'greeting' is the definition.
(I've seen this before)
'spies with initially obtuse' is the wordplay.
'spies' becomes 'CIA' (Central Intelligence Agency).
'with' means one lot of letters go next to another.
'initially' indicates taking the first letters.
The first letter of 'obtuse' is 'o'.
'cia'+'o'='CIAO'
(Other definitions for ciao that I've seen before include "Italian hello-goodbye" , "Italian hello or goodbye" , "European greeting" , "parting word" , "Buongiorno o arrivederci" .)