Inoculation fluids (4)
I believe the answer is:
sera
'inoculation fluids' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sera that I've seen before include "Bodily fluids (following 'que'?)" , "Watery liquids" , "Hospital supplies" , "Sear with serums" .)