Home with trees arranged in small group (9)
I believe the answer is:
threesome
'small group' is the definition.
(I've seen this before)
'home with trees arranged' is the wordplay.
'with' means one lot of letters go next to another.
'arranged' indicates anagramming the letters (letters rearranged).
'home'+'trees'='hometrees'
'hometrees' with letters rearranged gives 'THREESOME'.
'in' is the link.
(Other definitions for threesome that I've seen before include "triplets, perhaps?" , "One more than a couple" , "Blind mice, perhaps" , "The Fates, perhaps" , "Chekhov's sisters" .)