Aid sent off as an alternative (7)
I believe the answer is:
'as an alternative' is the definition.
'aid sent off' is the wordplay.
'off' is an anagram indicator.
'aidsent' is an anagram of 'INSTEAD'.
(Other definitions for instead that I've seen before include "Rather - detains (anag)" , "Stained (anag)" , "use this as a replacement" , "In place (of)" , "As a substitute" .)