Occupy sailor absorbed by popular success (7)
I believe the answer is:
inhabit
'occupy' is the definition.
('inhabit' can be a synonym of 'occupy')
'sailor absorbed by popular success' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'absorbed by' indicates putting letters inside.
'popular' becomes 'in'.
'success' becomes 'hit' (hit is a kind of success).
'in'+'hit'='inhit'
'ab' inserted into 'inhit' is 'INHABIT'.
(Other definitions for inhabit that I've seen before include "Occupy - settle" , "people" , "Live in (a place)" , "Occupy (dwelling)" , "Tenant" .)