Fruit held by some Londoners (5)
I believe the answer is:
melon
'fruit' is the definition.
(type of fruit)
'held by some londoners' is the wordplay.
'held by' indicates the answer is hidden within the clue.
'MELON' can be found hidden inside 'some londoners'.
(Other definitions for melon that I've seen before include "Sweet juicy gourd" , "Type of fruit" , "Large vine fruit" , "Fruit of the gourd family with a hard rind and juicy flesh" , "Large round fruit" .)