Left home, absorbed by island's horizon (7)
I believe the answer is:
Here is my best explanation:
'horizon' is the definition.
('skyline' can be a synonym of 'horizon')
'left home absorbed by island's' is the subsidiary indication.
'left' becomes 'l' (common abbreviation).
'home' becomes 'in' ('he's home' can mean 'he's in').
'absorbed by' is an insertion indicator.
'island' becomes 'skye' (**).
'lin' placed into 'skye' is 'skyline'.
(Other definitions for skyline that I've seen before include "Silhouette or outline of buildings", "Visible horizon", "Built-up horizon", "City horizon", "Horizon; like NY's (anag.)" and "Outline of hills or buildings against firmament".)