Grocer has a bird (3)
I believe the answer is:
roc
'a bird' is the definition.
(mythological bird of prey)
'grocer has' is the wordplay.
'has' indicates a hidden word.
'ROC' is hidden within 'grocer'.
(Other definitions for roc that I've seen before include "Sinbad's giant bird" , "Fabulous Eastern bird of some ferocity" , "Gigantic bird of Arabian legend" , "Legendary thing" , "Bird imagined" .)