Fruit held up by frail guy (4)
I believe the answer is:
ugli
'fruit' is the definition.
(I know that Ugli is a fruit)
'held up by frail guy' is the wordplay.
'up by' says the letters should be written in reverse.
'held' indicates a hidden word.
'ilgu' can be found hidden inside 'frail guy'.
'ilgu' reversed gives 'UGLI'.
(Other definitions for ugli that I've seen before include "Large juicy fruit with thick wrinkled skin" , "Hybrid fruit, sounds nasty" , "Orange-grapefruit cross" , "Trademarked hybrid citrus fruit" , "Jamaican form of 6" .)