Ring around one twisted tree (5)
I believe the answer is:
lilac
'one twisted tree' is the definition.
'lilac' can be an answer for 'tree' (I've seen this before). I'm not certain of the 'one twisted' bit.
'ring around' is the wordplay.
'ring' becomes 'lila' (I can't explain this - if you can you should give a lot more credence to this answer).
'around' becomes 'c' (abbreviation for 'circa').
'lila'+'c'='LILAC'
(Other definitions for lilac that I've seen before include "Shrub with fragment purple or white flowers" , "Tree - pinkish-purple colour" , "Shrub with fragrant purplish or white flowers" , "Syringa vulgaris, light purple in colour" , "Tree with purple or white flowers" .)