Guy has to leave fruit (5)
I believe the answer is:
mango
'fruit' is the definition.
(type of fruit)
'guy has to leave' is the wordplay.
'guy' becomes 'man' (guy can informally mean a man).
'has' means one lot of letters go next to another.
'to leave' becomes 'go' (to go is to depart or leave).
'man'+'go'='MANGO'
(Other definitions for mango that I've seen before include "Asian fruit" , "Large oval tropical fruit" , "fruit tree" , "Once exotic fruit" , "Type of fruit" .)