Fluid storage of convenience first found in Geneva lab (7)
I believe the answer is:
cistern
'fluid storage of convenience' is the definition.
I can't judge whether this definition defines the answer.
'first found in geneva lab' is the wordplay.
'first' becomes 'ist' (ist resembles cst).
'found in' indicates putting letters inside.
'geneva lab' becomes 'cern' (I can't justify this - if you can you should give a lot more credence to this answer).
'ist' placed within 'cern' is 'CISTERN'.
Can you help me to learn more?
(Other definitions for cistern that I've seen before include "Water storage tank" , "Vat" , "Water container" , "Tank, reservoir" , "Tank - sac of body fluid" .)