Scientists room (3)
'scientist's room' is the definition.
(laboratory)
This is all the clue.
(Other definitions for lab that I've seen before include "Socialist" , "Room for scientist" , "Chemist's workroom" , "biology classroom?" , "Dog" .)
(Other definitions for laboratory that I've seen before include "Where one investigates" , "Place of scientific research" , "Experimental area" , "Place for experimentation" , "Language-learning facility" .)