Send back green oranges perhaps not one for fighting over ground (4,3)
I believe the answer is:
turf war
'fighting over ground' is the definition.
(a fight over territory)
'send back green oranges perhaps not one' is the wordplay.
'send back' says the letters should be written backwards.
'green' becomes 'raw' (both can mean naive or inexperienced).
'oranges perhaps' becomes 'fruit' (oranges are fruit).
'not' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'raw'+'fruit'='rawfruit'
'rawfruit' with 'i' removed is 'rawfrut'.
'rawfrut' reversed gives 'TURF WAR'.
'for' is the link.
(Other definitions for turf war that I've seen before include "Territorial struggle between gangs" , "Dispute over territory between rival gangs" , "contest in which gangs participate?" , "Serious horse racing" , "territorial dispute" .)