Experimental glassware needed? Try underground (4,4)
I believe the answer is:
test tube
'experimental glassware' is the definition.
(I've seen this before)
'needed? try underground' is the wordplay.
'needed? try' becomes 'test' (synonyms. I am not sure about the 'needed?' bit.).
'underground' becomes 'tube' (the London Underground is nicknamed the Tube).
'test'+'tube'='TEST-TUBE'
Can you help me to learn more?
(Other definitions for test tube that I've seen before include "scientific birthplace" , "Small glass cylinder with one end closed, used in laboratory" , "Glass container in the laboratory" , "that's used in experiment supervised by 14 across [SCIENCE MASTER] , perhaps" , "Ling glass cylinder used in laboratories" .)