Fruit gives a guy energy (5)
I believe the answer is:
mango
'fruit' is the definition.
(type of fruit)
'a guy energy' is the wordplay.
'a guy' becomes 'man' (guy can informally mean a man).
'energy' becomes 'go' (I've seen this in other clues).
'man'+'go'='MANGO'
'gives' acts as a link.
(Other definitions for mango that I've seen before include "fruit-tree" , "Asian fruit" , "Large oval tropical fruit" , "Fruit, often in chutney" , "Tropical fruit, its pickle" .)