Get off on smut, worried after I'd returned (8)
I believe the answer is:
dismount
'get off' is the definition.
('dismount' can be a synonym of 'get off')
'on smut worried after i'd returned' is the wordplay.
'worried' is an anagram indicator.
'after' says to put letters next to each other.
'returned' is a reversal indicator.
'id' back-to-front is 'di'.
'on'+'smut'='onsmut'
'onsmut' with letters rearranged gives 'smount'.
'smount' after 'di' is 'DISMOUNT'.
(Other definitions for dismount that I've seen before include "Get off one's horse" , "Get down, from bike or horse" , "Alight from a horse or bicycle" , "Desert Arab perhaps" , "Get off a horse/bicycle" .)