Colourless liquid, while in palm, spilt (6)
I believe the answer is:
plasma
'colourless liquid' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'while in palm spilt' is the wordplay.
'while' becomes 'as' (eg 'while I walked' means 'as I walked').
'in' means one lot of letters goes inside another.
'spilt' indicates anagramming the letters.
'palm' anagrammed gives 'plma'.
'as' placed into 'plma' is 'PLASMA'.
Can you help me to learn more?
(Other definitions for plasma that I've seen before include "Hot ionised gas" , "element of transfusion" , "Colourless fluid in which blood cells are suspended" , "hot stuff" , "Yellow liquid in blood" .)