Uncle cuts up cactus? (9)
I believe the answer is:
succulent
'cactus?' is the definition.
(cactus is a kind of succulent)
'uncle cuts up' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'uncle'+'cuts'='unclecuts'
'unclecuts' is an anagram of 'SUCCULENT'.
(Other definitions for succulent that I've seen before include "Lush" , "Luscious" , "Eg, a cactus" , "Full of juice" , "One may be potted!" .)