Trendy berry is a CIA plot (4)
I believe the answer is:
acai
'trendy berry' is the definition.
(I've seen this in another clue)
'a cia plot' is the wordplay.
'plot' indicates an anagram (I've seen this in other clues).
'cia' with letters rearranged gives 'cai'.
'a'+'cai'='ACAI'
'is' is the link.
(Other definitions for acai that I've seen before include "fruit which is nutritious" , "South American palm tree" , "something nutritional to eat" , "South American food product" .)