custard apple vs fruit tree

custard apple and fruit tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
custard apple	Yes	No	No	No
fruit tree	Yes	No	No	No

As nouns, fruit tree is a hypernym of custard apple; that is, fruit tree is a word with a broader meaning than custard apple:

custard apple: any of several tropical American trees bearing fruit with soft edible pulp
fruit tree: tree bearing edible fruit

custard apple (noun)	fruit tree (noun)
the fruit of any of several tropical American trees of the genus Annona having soft edible pulp	tree bearing edible fruit
any of several tropical American trees bearing fruit with soft edible pulp