Doreen's injured back (7)
I believe the answer is:
endorse
'back' is the definition.
(back can mean to support or endorse)
'doreen's injured' is the wordplay.
'injured' indicates an anagram.
'doreens' with letters rearranged gives 'ENDORSE'.
(Other definitions for endorse that I've seen before include "No reeds (anag)" , "Give support or approval to" , "Sanction -- red nose (anag)" , "Express approval" , "Approve of, sign on back as of cheque" .)