Sailor with broken arm, almost completely inert (7)
I believe the answer is:
mariner
'sailor' is the definition.
(mariner is a kind of sailor)
'broken arm almost completely inert' is the wordplay.
'broken' indicates an anagram.
'almost completely' means to remove the last letter.
'inert' with its final letter removed is 'iner'.
'arm' with letters rearranged gives 'mar'.
'mar'+'iner'='MARINER'
'with' acts as a link.
(Other definitions for mariner that I've seen before include "'''The Rime of the Ancient ...'' (Coleridge) (7)'" , "Sailor" , "Seaman" , "Jack" , "Person sailing" .)