May dread disturbing reverie (8)
I believe the answer is:
daydream
'reverie' is the definition.
('daydream' can be a synonym of 'reverie')
'may dread disturbing' is the wordplay.
'disturbing' is an anagram indicator.
'may'+'dread'='maydread'
'maydread' with letters rearranged gives 'DAYDREAM'.
(Other definitions for daydream that I've seen before include "Diurnal reveries" , "A pleasant diurnal fantasy" , "(Indulge in) idle reverie" , "Indulge in a fantasy" , "Wool-gather" .)