Pollarded tree forms curved structure (4)
I believe the answer is:
arch
This might be a double definition.
'pollarded tree' is the first definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs sometimes mean the same thing.
'curved structure' is the second definition.
(architectural structure)
'forms' acts as a link.
Can you help me to learn more?
(Other definitions for arch that I've seen before include "Teasing; part of foot" , "Masonry construction for spanning an opening" , "architectural feature" , "not to go straight?" , "Way though - on foot!" .)