Jab from Ali, one needing cut treated (9)
I believe the answer is:
inoculate
'jab' is the definition.
(I know that jab can be written as inoculate)
'ali one needing cut treated' is the wordplay.
'needing' means one lot of letters go next to another.
'treated' indicates an anagram.
'ali'+'one'+'cut'='alionecut'
'alionecut' is an anagram of 'INOCULATE'.
'from' is the link.
(Other definitions for inoculate that I've seen before include "Immunise, vaccinate" , "to prevent infection" , "Induce immunity" , "Immunise with antigens" , "Treat with a vaccine or serum" .)