Is curt about kind of fruit tree (6)
I believe the answer is:
citrus
'kind of fruit tree' is the definition.
'is curt about' is the wordplay.
'about' is an anagram indicator.
'is'+'curt'='iscurt'
'iscurt' is an anagram of 'CITRUS'.
(Other definitions for citrus that I've seen before include "Describing lemons, for example" , "Orange, lime are such fruit" , "Type of tree bearing acidic fruit" , "Lemons, limes, oranges etc." , "sort of fruit tree" .)