Alienated eccentric caught in regular eddy (9)
I believe the answer is:
estranged
'alienated' is the definition.
('estrange' can be a synonym of 'alienate')
'eccentric caught in regular eddy' is the wordplay.
'eccentric' becomes 'strange' (synonyms).
'caught in' means one lot of letters goes inside another.
'regular' means one should take alternating letters.
The alternating letters of 'eddy' are 'ed'.
'strange' going within 'ed' is 'ESTRANGED'.
(Other definitions for estranged that I've seen before include "Having become unfriendly or alienated" , "Cut off" , "Alienated, disaffected" , "no longer friendly" , "Sad regent (anag) - disaffected" .)