A walk in the park — then get on a tree (8)
I believe the answer is:
Here is my best explanation:
'tree' is the definition.
(cinchona tree is a kind of tree)
'a walk in the park then get on a' is the wordplay.
'a walk in the park' becomes 'cinch' (I've seen this before).
'then get' is a charade indicator (letters next to each other).