International transport system, part of experiment? (4,4)
I believe the answer is:
test tube
'part of experiment?' is the definition.
'test tube' can be an answer for 'experiment?' (I've seen this before). I'm not certain of the 'part of' bit.
'international transport system' is the wordplay.
'international' becomes 'test' (I've seen this before).
'transport system' becomes 'tube' (I've seen this before).
'test'+'tube'='TEST-TUBE'
Can you help me to learn more?
(Other definitions for test tube that I've seen before include "Laboratory instrument" , "Laboratory glassware" , "Laboratory experimental container" , "Laboratory item (for babies?)" , "Lab vessel" .)