Age of exotic tree, tiny (8)
I believe the answer is:
eternity
'age' is the definition.
(I've seen this before)
'exotic tree tiny' is the wordplay.
'exotic' indicates anagramming the letters (an unusual form of the letters).
'tree'+'tiny'='treetiny'
'treetiny' is an anagram of 'ETERNITY'.
'of' acts as a link.
(Other definitions for eternity that I've seen before include "Forever and ever" , "destination of film?" , "Type of ring" , "timelessness" , "the poet palmed in an hour?" .)