It's fruit that gives a chap energy (5)
I believe the answer is:
mango
'it's fruit' is the definition.
(type of fruit)
'a chap energy' is the wordplay.
'a chap' becomes 'man' (chap can mean a man).
'energy' becomes 'go' (go can mean energy or enthusiasm).
'man'+'go'='MANGO'
'that gives' is the link.
(Other definitions for mango that I've seen before include "Once exotic fruit" , "product" , "Fleshy tropical fruit" , "Type of fruit" , "Asian fruit" .)