Groceries include flyer (3)
I believe the answer is:
roc
'flyer' is the definition.
(I have seen 'Legendary flyer' mean 'roc' so perhaps 'flyer' could also mean 'roc')
'groceries include' is the wordplay.
'include' indicates the answer is hidden within the clue.
'ROC' is hidden within 'groceries'.
(Other definitions for roc that I've seen before include "fabulous bird is seen" , "Gigantic bird of eastern legend - cor!" , "Fabulous Eastern bird of some ferocity" , "Bird imagined" , "Sinbad's monster bird" .)