Chlorofluorocarbon said to protect small tree (6)
I believe the answer is:
bonsai
'small tree' is the definition.
(I've seen this before)
'chlorofluorocarbon said to protect' is the wordplay.
'to protect' says the answer is hidden in the clue (the answer is protected by the clue).
'BONSAI' can be found hidden inside 'chlorofluorocarbon said'.
(Other definitions for bonsai that I've seen before include "Tiny Japanese tree" , "Japanese craft of growing dwarf trees" , "small growth" , "(Cultivation of) dwarf trees" , "Potted tree or shrub artificially prevented from reaching normal size" .)