Layer helping lab test (9)
I believe the answer is:
titration
'lab test' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'layer helping' is the wordplay.
'layer' becomes 'tit' (I am not sure about this - if you are sure you should believe this answer much more).
'helping' becomes 'ration' (a ration is a serving or helping).
'tit'+'ration'='TITRATION'
Can you help me to learn more?
(Other definitions for titration that I've seen before include "Process used by chemist" , "lab procedure" .)