Fleshy fruit, first of peaches (5)
I believe the answer is:
plump
'fleshy' is the definition.
(plump can mean fleshy or fat)
'fruit first of peaches' is the wordplay.
'fruit' becomes 'plum' (plum is a kind of fruit).
'first of peaches' becomes 'p' (1st letter of 'peaches').
'plum'+'p'='PLUMP'
(Other definitions for plump that I've seen before include "Opt - round" , "Corpulent" , "Fat - fatten" , "Slightly fat" , "Choose; chubby" .)