One that's finished work on Hebridean island (7)
I believe the answer is:
'one that's finished work' is the definition.
I can't tell whether this defines the answer.
'on hebridean island' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'hebridean island' becomes 'tiree' (island of the Hebrides).
Can you help me to learn more?
(Other definitions for retiree that I've seen before include "One stopping work" , "Someone no longer working" , "Person out of work" , "Pensioner" , "One who has ceased to work" .)