Leave coat by Irish lake (8)
I believe the answer is:
furlough
'leave' is the definition.
(furlough is a kind of leave)
'coat by irish lake' is the wordplay.
'coat' becomes 'fur coat' (fur coat is a kind of coat).
'by' says to put letters next to each other.
'irish lake' becomes 'lough' (Irish term for 'lake').
'fur'+'lough'='FURLOUGH'
(Other definitions for furlough that I've seen before include "Very unattractive" , "Leave of absence from military duties" , "Temporary leave of absence from military duty" .)