Cat and bat in tree (5,6)
I believe the answer is:
pussy willow
'in tree' is the definition.
(I've seen this before)
'cat and bat' is the wordplay.
'cat' becomes 'pussy' (pussy can mean a cat).
'and' says to put letters next to each other.
'bat' becomes 'willow' (I've seen this before).
'pussy'+'willow'='PUSSY-WILLOW'
(Other definitions for pussy willow that I've seen before include "American tree with silvery catkins" , "Leaving body" , "Tree with silky grey catkins" , "Plant bearing catkins" , "Catkin tree" .)