Motto revised to include a love apple (6)
I believe the answer is:
tomato
'love apple' is the definition.
(synonyms)
'motto revised to include a' is the wordplay.
'revised' indicates anagramming the letters.
'to include' is an insertion indicator.
'motto' is an anagram of 'tomto'.
'tomto' placed around 'a' is 'TOMATO'.
(Other definitions for tomato that I've seen before include "It used to be call a love-apple" , "Fruit-vegetable" , "Red fruit eaten as veg" , "A motto turned out to be fruit/veg" , "Type of sauce" .)