Curved shapes in pollarded trees (6)
I believe the answer is:
arches
'curved shapes' is the definition.
(arch is a kind of curved shape)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for arches that I've seen before include "Curves over openings" , "Vaults" , "Parts of bridge structure" , "Found on feet and bridges" , "(Cat) stretches (back)" .)