Called out robust greeting (4)
I believe the answer is:
hail
'greeting' is the definition.
(hail is a kind of greeting)
'called out robust' is the wordplay.
'called out' shows a homophone (sound like).
'robust' becomes 'hale' (in good health).
'hale' is a homophone of 'HAIL'.
(Other definitions for hail that I've seen before include "Old Roman salute, or frozen pellets" , "Stones from the sky" , "Greet loudly" , "Signal to and summon, say a taxi" , "Welcome - cold shower" .)