Tiny tree flowering forever (8)
I believe the answer is:
eternity
'forever' is the definition.
(synonyms)
'tiny tree flowering' is the wordplay.
'flowering' is an anagram indicator (letters develop or 'flower' into another form).
'tiny'+'tree'='tinytree'
'tinytree' anagrammed gives 'ETERNITY'.
(Other definitions for eternity that I've seen before include "Wolfgang Amadeus -" , "timelessness" , "That's a very long time" , "Endless time" , "Time after death" .)