Tissue bather (5)
I believe the answer is:
lymph
'tissue bather' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lymph that I've seen before include "Fluid containing antibodies" , "Colourless fluid with white blood cells" , "Bodily fluid" , "Watery fluid containing white blood cells" , "Body fluid" .)