Curve of a conifer with its top cut off (4)
I believe the answer is:
arch
'curve' is the definition.
(synonyms)
'a conifer with its top cut off' is the wordplay.
'a conifer' becomes 'larch' (larch is a kind of conifer).
'with its top cut off' means to remove the first letter.
'larch' with its first letter taken away is 'ARCH'.
'of' is the link.
(Other definitions for arch that I've seen before include "Vaulted opening" , "Playfully superior" , "Curved part of the foot" , "Supporting structure" , "Masonry construction for spanning an opening" .)