Overburdened boat crew outwardly united (8)
I believe the answer is:
weighted
'overburdened' is the definition.
(thesaurus)
'boat crew outwardly united' is the wordplay.
'boat crew' becomes 'eight' (crew of eight rowers).
'outwardly' is an insertion indicator (some letters go outside others).
'united' becomes 'we'd' (united in marriage).
'eight' inserted within 'wed' is 'WEIGHTED'.
(Other definitions for weighted that I've seen before include "Made heavier" , "loaded" , "Given a bias" , "having extra burden to carry" .)