Try piece of rigatoni as part of experiment (4,4)
I believe the answer is:
test tube
'experiment' is the definition.
(I've seen this before)
'try piece of rigatoni as' is the wordplay.
I cannot really understand how this works, but
'try' could be 'test' (synonyms) and 'test' is present in the answer.
'piece' could be 'tube' (tube is a kind of piece) and 'tube' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'part of' acts as a link.
Can you help me to learn more?
(Other definitions for test tube that I've seen before include "Hollow cylinder for the laboratory" , "Glass item in lab" , "Scientist's cylindrical glass" , "Lab vessel" , "Experimental glassware" .)