Show movement in a tree top (8)
I believe the answer is:
operetta
'show' is the definition.
(I've seen this before)
'movement in a tree top' is the wordplay.
'movement in' indicates anagramming the letters (I've seen this in other clues).
'a'+'tree'+'top'='atreetop'
'atreetop' anagrammed gives 'OPERETTA'.
(Other definitions for operetta that I've seen before include "Type of musical drama" , "La belle Helene, say" , "Light musical drama" , "Show" , "G&S work, perhaps" .)