Family gathering is not real (9)
I believe the answer is:
relations
'family' is the definition.
(I've seen this before)
'gathering is not real' is the wordplay.
'gathering' indicates an anagram (letters gathered in a new way).
'is'+'not'+'real'='isnotreal'
'isnotreal' with letters rearranged gives 'RELATIONS'.
(Other definitions for relations that I've seen before include "accounts" , "They're connected by blood or marriage" , "kindred?" , "Kith" , "Sex" .)