In short, the party of experiment? (3)
I believe the answer is:
lab
This clue might be a double definition.
'in short' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'party of experiment?' is the second definition.
'lab' can be an answer for 'party' (abbreviation for Labour). I am not certain of the 'of experiment?' bit.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for lab that I've seen before include "Research workroom" , "Scientific research space, in short" , "In brief, a room for scientific experiments" , "Scientist's workroom" , "Socialist" .)