Cast off in small body of water around Dublin (6)
I believe the answer is:
slough
This might be a double definition.
'cast off in small' is the first definition.
'slough' can be an answer for 'cast' (sloughing is a kind of casting). I am unsure of the 'off in small' bit.
'body of water around dublin' is the second definition.
(Irish term for 'lake')
Can you help me to learn more?
(Other definitions for slough that I've seen before include "Swamp; shed (dead skin)" , "where friendly bombs were wanted" , "Swamp; Berkshire town" , "Swamp; cast off (skin)" , "Swamp or marshy place, maybe of despond" .)