Sticky substance (3)
'sticky substance' is the definition.
(goo is a slimy or sticky substance)
This is the entire clue.
(Other definitions for goo that I've seen before include "Sticky substance (sl.)" , "Substance that's viscous" , "Sticky substance (colloq.)" , "Sticky matter" , "syrup" .)
'sticky substance' is the definition.
(I've seen this in another clue)
This is the entire clue.