Excellent man on island holiday (4,6)
I believe the answer is:
good friday
'holiday' is the definition.
(I know that Good Friday is a type of Christian holy day)
'excellent man on island' is the wordplay.
'excellent' becomes 'good'.
'man on island' becomes 'Friday' (Man Friday, character in the novel Robinson Crusoe).
'good'+'friday'='GOOD FRIDAY'
(Other definitions for good friday that I've seen before include "Christian festival" , "date" , "religious occasion" .)