Give a jab turning into a clue (9)
I believe the answer is:
inoculate
'give a jab' is the definition.
(I've seen this before)
'turning into a clue' is the wordplay.
'turning' indicates an anagram.
'into'+'a'+'clue'='intoaclue'
'intoaclue' with letters rearranged gives 'INOCULATE'.
(Other definitions for inoculate that I've seen before include "Inject against a disease" , "Induce immunity" , "Treat with a vaccine or serum" , "Immunise with antigens" , "to prevent infection" .)