Some Londoners devour fruit (5)
I believe the answer is:
melon
'fruit' is the definition.
(melon is a kind of fruit)
'some londoners devour' is the wordplay.
'devour' says the answer is hidden in the clue (the answer has been devoured by the clue).
'MELON' is hidden in the letters of 'some londoners'.
(Other definitions for melon that I've seen before include "Type of fruit" , "I'm very seedy" , "Large round fruit" , "Sweet juicy gourd" , "Cantaloupe fruit" .)