Cryptic clue, say, put in tree (10)
I believe the answer is:
eucalyptus
'tree' is the definition.
(eucalyptus is a kind of tree)
'cryptic clue say put' is the wordplay.
'cryptic' indicates an anagram (a cryptic or obscure order of the letters).
'clue'+'say'+'put'='cluesayput'
'cluesayput' anagrammed gives 'EUCALYPTUS'.
'in' acts as a link.
(Other definitions for eucalyptus that I've seen before include "Australian tree yielding gum and oil" , "Evergreen tree" , "Australasian tree" .)