One keen to eat arrested in Erith stores (5)
I believe the answer is:
diner
'one keen to eat' is the definition.
(someone dining at a restaurant)
'arrested in erith stores' is the wordplay.
'stores' indicates the answer is hidden within the clue.
'DINER' can be found hidden inside 'arrested in erith'.
(Other definitions for diner that I've seen before include "American restaurant" , "Buffet car" , "(One using) restaurant car" , "(Person eating in) restaurant" , "US cafe" .)