Cast off and start sailing the Irish lake (6)
I believe the answer is:
slough
'cast off' is the definition.
(sloughing is a kind of casting off)
'start sailing the irish lake' is the wordplay.
'start' says to take the initial letters.
'the irish lake' becomes 'lough' (I've seen this before).
The first letter of 'sailing' is 's'.
's'+'lough'='SLOUGH'
'and' is the link.
(Other definitions for slough that I've seen before include "Swamp; shed (dead skin)" , "poet wanted destroyed" , "Swamp; cast off (skin)" , "Swamp or marshy place, maybe of despond" , "A bog or marsh, perhaps of despond" .)