Dome of larches (4)
I believe the answer is:
arch
'dome' is the definition.
(thesaurus)
'of larches' is the wordplay.
'of' indicates the answer is hidden within the clue.
'ARCH' is hidden in the letters of 'larches'.
(Other definitions for arch that I've seen before include "Curve that spans an opening" , "Structural curve" , "Vault; roguish" , "Affectedly playful like senior angel" , "Affectedly playful like curved structure" .)