Company brought in to inoculate sheep (5)
I believe the answer is:
jacob
'sheep' is the definition.
(I've seen this before)
'company brought in to inoculate' is the wordplay.
'company' becomes 'co' (abbreviation).
'brought in to' means one lot of letters goes inside another.
'inoculate' becomes 'jab' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'co' inserted into 'jab' is 'JACOB'.
Can you help me to learn more?
(Other definitions for jacob that I've seen before include "Esau's twin brother" , "Biblical son of Isaac" , "man" , "Smooth character" , "Bible character - old breed of sheep" .)